Ultrasonic rock sampling using longitudinal–torsional vibrations

In the last years several European and US space projects have been focused on the development of surface rovers for planetary missions, such as ExoMars and Mars Exploration Rovers. The main function of these vehicles consists of moving across planet surfaces, and drilling and retrieving samples for in situ analysis.Recent research has shown that drilling of rock materials can be achieved using axially oscillating tuned devices which, compared with conventional rotary drills, operate at lower power and highly reduced preload requirements. As a result, at present, ultrasonics is considered a very promising technology for exobiological prospecting.In this work, two novel ultrasonic rock samplers, both operating in a longitudinal–torsional composite mode, are proposed along with the conceptual design of a full coring apparatus, for preload delivery and core removal. To assess the penetration capability of the excited composite vibrations, preliminary drilling trials were conducted. Since sand constitutes a significant portion of the Martian surface, sandstone was used in the trials.     

Propagation of Lamb waves in pure longitudinal modes

I.IntroductionSinceLambwaveshavewideaPplicationinnondestructiveinspectionandsensors1interestsintheinvestigationofit8propagationaredeveloped.VictorovI1lhaspointedoutthatastohomogeneous,whformsolidplateinunersedillliquld,theverticaldisplacementoftheplate'ssurfaCemaybezerowhenthephasevelocityisequaltotheplatelongitudinalwavespeed.ThisconclusionhasimportantaPplication.RecelltlyPilaskietc.I2]aPproveditbyusing.thefree-boundaryLambwavtheoryandgavetheconditionstoreachit.ItisknownthatthedisaPpeara…     

Coupling of two defect modes in photonic crystal fibers

The coupling characteristics of two defect modes in photonic crystal fibers are investigated theoretically by the finite-difference time-domain (FDTD) method. The transmission spectrum and eigenmodes of optical wave are found to be very sensitive to the geometrical and physical parameters of the structure, as well as to the relative position of the two defects.     

Generation of new longitudinal modes in an amplifying dye solution

A novel phenomenon is reported for the first time that the generation of the newlongitudinal modes in amplifying multi-longitudinal mode laser in a dye amplifier.The newmodes are located on the violet side within the gain band of the amplifing medium.The phe-nomenon is explained by the theory of third-order nonlinear polarization in the case of four-wave resonances.The intensity of the new modes created are comparable with or even higherthan that of the original modes.The effect can be expected to serve as a new method for ex-tention of spectral tuning ranges of laser.     

Absorption effects on the longitudinal bulk plasmon–polariton modes in 1D heterostructures containing anisotropic metamaterials

The transmission properties of electromagnetic waves through a one-dimensional layered system containing alternate layers of air and a uniaxial anisotropic left-handed material are investigated. The optical axis of such heterostructure is along the stacking direction and the components of the electric permittivity and magnetic permeability tensors that characterize the metamaterial are modeled by a Drude-type response and a split-ring resonator metamaterial response, respectively. Different plasmon frequencies are considered for directions parallel and perpendicular to the optical axis. For oblique incidence, longitudinal bulk-like plasmon polariton modes are found in the neighborhood of the plasmon frequency along the optical axis and anisotropy leads to the unfolding of nearly dispersionless plasmon–polariton bands either above or below the plasmon frequency. Moreover, it is shown that, even in the presence of loss/absorption, these plasmon polariton modes do survive and, therefore, should be experimentally detected.     

Solar magnetohydrodynamic modes and parametric resonance in neutrino spin–flavor conversion

Consequences of parametric resonances on neutrino resonant spin–flavor precession (RSFP) arising from global magnetohydrodynamic waves in the Sun are investigated. We show that for typical magnetic field profiles which generate an RSFP solution to the solar neutrino anomaly, the effects of the parametric resonance can be found for neutrinos of which the energy is of order 0.1 to 1 MeV. This opens the possibility of investigating these effects using real time experiments, like Borexino or Hellaz. Received: 4 March 1999 / Published online: 8 December 1999     

Superfluidity and collective modes in Rashba spin–orbit coupled Fermi gases

We present a theoretical study of the superfluidity and the corresponding collective modes in two-component atomic Fermi gases with s$s$-wave attraction and synthetic Rashba spin–orbit coupling. The general effective action for the collective modes is derived from the functional path integral formalism. By tuning the spin–orbit coupling from weak to strong, the system undergoes a crossover from an ordinary BCS/BEC superfluid to a Bose–Einstein condensate of rashbons. We show that the properties of the superfluid density and the Anderson–Bogoliubov mode manifest this crossover. At large spin–orbit coupling, the superfluid density and the sound velocity become independent of the strength of the s$s$-wave attraction. The two-body interaction among the rashbons is also determined. When a Zeeman field is turned on, the system undergoes quantum phase transitions to some exotic superfluid phases which are topologically nontrivial. For the two-dimensional system, the nonanalyticities of the thermodynamic functions and the sound velocity across the phase transition are related to the bulk gapless fermionic excitation which causes infrared singularities. The superfluid density and the sound velocity behave nonmonotonically: they are suppressed by the Zeeman field in the normal superfluid phase, but get enhanced in the topological superfluid phase. The three-dimensional system is also studied.     

Homological perspective on edge modes in linear Yang–Mills and Chern–Simons theory

Letters in Mathematical Physics - We provide an elegant homological construction of the extended phase space for linear Yang–Mills theory on an oriented and time-oriented Lorentzian manifold...     

Coupling between velocity and interface perturbations in cylindrical Rayleigh–Taylor instability

Rayleigh–Taylor instability(RTI) in cylindrical geometry initiated by velocity and interface perturbations is investigated analytically through a third-order weakly nonlinear(WN) model. When the initial velocity perturbation is comparable to the interface perturbation, the coupling between them plays a significant role. The difference between the RTI growth initiated only by a velocity perturbation and that only by an interface perturbation in the WN stage is negligibly small. The effects of the mode number on the first three harmonics are discussed respectively. The low-mode number perturbation leads to large amplitudes of RTI growth. The Atwood number and initial perturbation dependencies of the nonlinear saturation amplitude of the fundamental mode are analyzed clearly. When the mode number of the perturbation is large enough,the WN results in planar geometry are recovered.     

Multiresonance modes in sine–Gordon brane models

In this work, we study the localization of the vector gauge field in two five-dimensional braneworlds generated by scalar fields coupled to gravity. The sine–Gordon like potentials are employed to produce different thick brane setups. A zero mode localized is obtained, and we show the existence of reverberations with the wave solutions indicating a quasi-localized massive mode. More interesting results are achieved when we propose a double sine–Gordon potential to the scalar field. The resulting thick brane shows a more detailed topology with the presence of an internal structure composed by two kinks. The massive spectrum of the gauge field is revalued on this scenario revealing the existence of various resonant modes. Furthermore, we compute the corrections to Coulomb law coming from these massive KK vector modes in these thick scenarios, which is concluded that the dilaton parameter regulates these corrections.     

Anisotropic Magnon–Magnon Coupling in Synthetic Antiferromagnets

Magnon-magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies.To induce magnon-magnon coupling,the parity symmetry between two magnetization needs to be broken.Here we experimentally demonstrate a convenient method to break the parity symmetry by the asymmetric structure.We successfully introduce a magnon-magnon coupling in Ir-based synthetic antiferromagnets CoFeB(10 nm)/Ir(t_(Ir)=0.6 nm,1.2 nm)/CoFeB(13 nm).Remarkably,we find that the weakly uniaxial anisotropy field(～20 Oe) makes the magnon-magnon coupling anisotropic.The coupling strength presented by a characteristic anticrossing gap varies in the range between 0.54 GHz and 0.90 GHz for t_(Ir)=0.6 nm,and between 0.09 GHz and 1.4 GHz for t_(Ir)=1.2 nm.Our results demonstrate a feasible way to induce magnon-magnon coupling by an asymmetric structure and tune the coupling strength by varying the direction of in-plane magnetic field.The magnon-magnon coupling in this highly tunable material system could open exciting perspectives for exploring quantum-mechanical coupling phenomena.     

Gravitational perturbation and quasi-normal modes of charged black holes in Einstein–Born–Infeld gravity

Born–Infeld electrodynamics has attracted considerable interest due to its relation to strings and D-branes. In this paper the gravitational perturbations of electrically charged black holes in Einstein–Born–Infeld gravity are studied. The effective potentials for axial perturbations are derived and discussed. The quasi normal modes for the gravitational perturbations are computed using a WKB method. The modes are compared with those of the Reissner–Nordström black hole. The relation of the quasi normal modes with the non-linear parameter and the spherical index are also investigated. Comments on stability of the black hole and on future directions are madeThis revised version was published online in April 2005. The publishing date was inserted.     

New bulk and surface phonon–plasmon modes in Raman spectra of porous n-InP

We report the Raman study of porous doped InP. The additional Raman bands were found in comparison with unporous doped InP. The effective medium theory is used to show that these bands may be assigned to a new coupled LO-phonon–plasmon mode and a contribution from surface polaritons.     

Average intensity and spreading of super Lorentz–Gauss modes in turbulent atmosphere

The super Lorentz–Gaussian (SLG) modes has been introduced to describe the radiation emitted by the multi-mode diode lasers. Here the propagation properties of SLG modes in turbulent atmosphere are investigated. Based on the extended Huygens–Fresnel integral and the Hermite–Gaussian expansion of a Lorentzian function, analytical formulae for the average intensities and the effective beam sizes of SLG₀₁ and SLG₁₁ modes are derived in turbulent atmosphere. The average intensity distribution and the spreading properties of SLG₀₁ and SLG₁₁ modes in turbulent atmosphere are numerically demonstrated. The influences of the beam parameters and the structure constant of the atmospheric turbulence on the propagation of SLG₀₁ and SLG₁₁ modes in turbulent atmosphere are also discussed in detail.     

Coupling effect in a near-field object–superlens system

The coupling effect in a near-field object–superlens system has been studied, where the object is a silver cylinder and the superlens is a silver slab. A semi-analytical formulation has been established to study the system with and without the coupling effect. The analysis shows that the coupling effect significantly changes the field distributions of both the object and the image, leading to the conclusion that such a system must be designed and analyzed as a whole. Our study also suggests that it is possible to design a superlens system with mismatched permittivities.     

Non-Local Coupling and Partial Synchronization in Chaotic Systems

Partial synchronization （PaS） on regular networks with a few non-local couplings are studied. The criterion that PaS can emerge in any given network and some relevant phenomena about Lyapunov exponents are found. Theoretical and numerical analysis show that the non-local coupling is the key mechanism of the emergence of PaS.     

End modes in arrays of modulated Su–Schrieffer–Heeger chains

In this article, an extended and modulated version of the classic Su–Schrieffer–Heeger model is analysed. The nature of the end modes and the effect of cyclic modulation of the hopping parameters are studied in detail. The analysis is extended to the case of an array of linear chains described by the Su–Schrieffer–Heeger model, where the robustness of the end states for a large range of coupling strengths between the chains is found.     

Analysis of surface and guided wave plasmon polariton modes in insulator–metal–insulator planar plasmonic waveguides

Theoretical and experimental study of the surface plasmon–polariton and guided wave plasmon polariton modes is presented for the Sapphire/Ag/Polycarbonate/Air structure. Theoretical results are obtained by solving complex multilayer eigenvalue equations as well as the reflectivity equation for this structure. It is proposed that the mode attenuation can be significantly reduced by inserting a low index dielectric buffer between the metal and the guiding dielectric layer. The dispersion and attenuation curves are generated. Both the surface plasmon and guided wave plasmon polariton modes are studied experimentally. The experimental values of the effective refractive indices agree well with the theoretical values. The electric field profiles are generated and used to examine the nature of modes. After optimization of various parameters the condition for low loss single mode guiding is obtained for the proposed structure. Effect of metal thickness on surface plasmon mode is also discussed. It is inferred that in a properly optimized plasmonic waveguide, the losses can be reduced by a factor of 4.     

Quantized longitudinal exciton-polaritons in periodic metal–semiconductor nanostructures

We theoretically investigate the optical properties of one-dimensional photonic crystals composed of two alternating layers, namely a semiconductor film and a metallic one. The nonlocal optical response of the semiconductor is here described by using a resonant excitonic dielectric function, whereas the local response function of the metal film is modeled with Drude formula. We calculate optical spectra of the metal–semiconductor 1D photonic crystal for both s- and p-polarization geometries. In both cases the spectra exhibit a rich resonance structure due to the coupling of size-quantized excitons inside the semiconductor film with light. We show the difference between s- and p-polarization reflectivity as the angle of incidence is increased. In the p-polarization geometry, besides transverse exciton-polariton modes, longitudinal polarization waves are excited producing additional spectral resonances. The spectra become radically different when the frequency corresponding to the minimum of the first photonic pass-band is close to the exciton resonance, since such a frequency is distinct for s- and p-polarized modes. We also show how reflectivity spectra for both polarizations are modified with varying the metal filling fraction which controls the width of the gap below the lowest frequency band.