Analysis of hot spots in deuterium plasma focus with SSNTD

Analysis of hot spots was conducted by using two kinds of pin-hole cameras, with LR-115 detectors. Hot spots emitting positive particles from nuclear processes were located. Their locations were compared with locations emitting soft X-ray. In this experiments neutron yield was ≈10⁸ n.     

Nonlinear dynamics of mechanical systems with friction contacts: Coupled static and dynamic Multi-Harmonic Balance Method and multiple solutions

Real applications in structural mechanics where the dynamic behavior is linear are rare. Usually, structures are made of components assembled together by means of joints whose behavior maybe highly nonlinear. Depending on the amount of excitation, joints can dramatically change the dynamic behavior of the whole system, and the modeling of this type of constraint is therefore crucial for a correct prediction of the amount of vibration.     

On the solutions of correlation equations for classical continuous systems

A method for solving the finite-volume Kirkwood-type correlation equations for tempered boundary conditions is developed. The central idea is an analytic continuation in the activity of the resolvent formulas for the solutions. The uniqueness theorem is proved for activities in a larger domain of the complex plane than the “standard” circle of analyticity¹). A connection with the eigenvector problem for the corresponding Kirkwood-type operators is discussed. We compare also the correlation equation method with the “equilibrium equation” one handling directly with the Gibbs probability measure.     

Acoustic timescale characterisation of symmetric and asymmetric multidimensional hot spots

In this work, two-dimensional hot spots are modelled by combining a linear temperature gradient with a constant temperature plateau. This approach retains the simplicity of a linear temperature gradient, but captures the effects of a local temperature maximum of finite size. Symmetric and asymmetric plateau regions are modelled using both rectangular and elliptical geometries. A one-step Arrhenius reaction for H₂–air is used to model the reactive mixture. Plateaus with different ratios of excitation to acoustic timescales, spanning two orders of magnitude, are simulated. Even with clear differences in behaviour between one and two dimensions, the a priori prescribed hot spot timescale ratio is shown to characterise the 2-D gasdynamic response. The relationship between one and two dimensions is explored using asymmetric plateau regions. It is shown that 1-D behaviour is recovered over a finite time. Furthermore, the duration of this 1-D behaviour is directly related to the asymmetry of the plateau.     

Hot electrons in nonparabolic bands with acoustic and polar optical phonon scattering

Most compound semiconductors have nonparabolic energy bands, and in pure material the dominant scattering mechanisms are usually by acoustic and polar optical phonons. In this paper, general expressions for the high-field transport properties of such materials are derived, using the balance-of-energy method and assuming a drifted Maxwellian distribution function. Under certain conditions the resultant drift velocity-field curves show a single-band negative differential resistance, arising not only from the increase in effective mass with carrier energy, but also from the change in relative scattering efficiencies of the two mechanisms as the applied field is increased. This effect is more marked at low temperatures. The model gives good agreement with previously reported experimental results on n-type PbTe at 77°K.     

The hot bands of silane between 2120 and 2270 cm

The infrared spectrum of the SiH₄ molecule has been recorded between 2040 and 2320 cm⁻¹ using the high-resolution Fourier interferometer of the Laboratoire de Photophysique Moléculaire (Orsay, France). The resolution was 5.4 × 10⁻³ cm⁻¹. In this region, many lines were previously analyzed and assigned to the ν₁/ν₃ stretching dyad of ²⁸SiH₄, ²⁹SiH₄, and ³⁰SiH₄ molecules [J. Mol. Spectrosc. 143 (1990) 35]. However, several lines in the spectrum were not assigned. The results obtained in our previous study [J. Mol. Spectrosc. 197 (1999) 307] of the infrared spectrum of ²⁸SiH₄, in the bending-stretching tetrad region at 3100 cm⁻¹, enabled us to assign 204 of the observed transitions to hot bands (the ν₁ + ν₂/ν₁ + ν₄/ν₂ + ν₃/ν₃ + ν₄ bending-stretching tetrad minus the ν₂/ν₄ bending dyad). These transitions were used to refine the set of the Hamiltonian parameters of the bending-stretching tetrad. The analysis is performed using the tensorial formalism developed in Dijon for tetrahedral molecules and implemented in the STDS software (http://www.u-bourgogne.fr/LPUB/shTDS.html).     

Infrared spectra of CS2: Measurement of “hot” bands associated with the 2325 cm−1 and 2962 cm−1 bands

The 12⁰1-00⁰0 and 02⁰1-00⁰0 transitions of CS₂ have been measured with a resolution of 0.025 cm^?1. The following “hot” bands associated with these transitions were also measured 13¹1?01¹0, 22⁰1? 10⁰0, 14⁰1?02⁰0, 14²1?02²0, 03¹1?01¹0, 12⁰1?10⁰0, 04⁰1?02⁰0, 04²1?02²0, 13¹1?11¹0, and 22⁰1?20⁰0. Improved rotational constants are given for the ground state and the first bending state. A consistent set of band constants is given for all the above vibrational transitions.     

Energy of optical polarons in systems with anisotropic energy bands

We consider a (band) electron-LO phonon system described by an anisotropic Fröhlich Hamiltonian. By means of functional integration techniques, the phonon terms can be eliminated exactly, leading to an effective one-particle problem. The (formal) free energy of this effective system is investigated. We clarify its asymptotic behaviour (that is the small- and large-coupling regime) and present Monte-Carlo results for the ground-state energy in the intermediate region. Finally, a comparison is drawn with previous work.     

Measurement of hot spots inside the proton at HERA and LEP/LHC

In this paper we discuss the measurement of regions in the proton where the density of small-x partons is large, called hot spots, by means of an associated jet analysis. An analytical estimate of the cross section is presented and the jet kinematics is discussed in the HERA and LEP-LHC frame. A Monte Carlo estimate shows that the number of jets produced in deep inelastic scattering events at HERA, suitable for this analysis, amounts to a few 1000 jcts for a data sample with an integrated luminosity of about 10 pb^–1.supported in part by FONDECYT 0367/90     

Transition from stick-slip to continuous sliding in atomic friction: entering a new regime of ultralow friction

A transition from stick-slip to continuous sliding is observed for atomically modulated friction by means of a friction force microscope. When the stick-slip instabilities cease to exist, a new regime of ultralow friction is encountered. The transition is described in the framework of the Tomlinson model using a parameter eta which relates the strength of the lateral atomic surface potential and the stiffness of the contact under study. Experimentally, this parameter can be tuned by varying the normal load on the contact. We compare our results to a recently discussed concept called superlubricity.     

Vibration of continuous systems with compliant boundaries

A theoretical study of two types of continuous systems with a general form of compliant boundary conditions is presented. The systems considered are elastic beams and circular plates with elastic damped edge constraints. Beam studies are restricted to those with identical boundary conditions at each end. The method of solution consists of formulating the edge condition of the system in terms of the impedance of the compliant boundary material and of using classical solution techniques to solve the equations of motion. The result of matching the boundary conditions of the system with constraining conditions is the system frequency equation in terms of the constraint impedances.A discussion is presented giving the influence of the compliant material on the vibration of the structure. The models give numerically the effect of elasticity and damping of the supports on the resonant frequencies of the systems. Parameters are obtained which indicate when one may assume simply supported or clamped boundaries for the actual case of elastic damped constraints without introducing large errors in the natural frequencies.     

Coherent control of nanoscale light localization in metamaterial: creating and positioning isolated subwavelength energy hot spots

We show the strong optically induced interactions between discrete metamolecules in a metamaterial system and coherent monochromatic continuous light beam with a spatially tailored phase profile can be used to prepare a subwavelength scale energy localization. Well-isolated energy hot spots of a fraction of a wavelength can be created and positioned on the metamaterial landscape offering new opportunities for data storage and imaging applications.     

Difference frequency laser spectroscopy of HCNH+: Observation of the isotopic species and the hot bands

The infrared spectra of the isotopic species of HCNH⁺, HCND⁺ and H¹³CNH⁺, have been observed with a difference frequency laser system. The r_s structure of the ion has been determined by combining the rotational constants of the normal species and DCNH⁺ previously obtained. Two hot bands of the normal species, presumably ν₁ + ν₄ ← ν₄ and ν₁ + ν₅ ← ν₅, have also been observed and the spectroscopic constants have been determined.     

Surface-enhanced Raman scattering substrates of high-density and high-homogeneity hot spots by magneto-metal nanoprobe assembling

Binary naoparticles composed of a superparamagnetic Fe(3)O(4) core and an Au nanoshell were prepared via a high-temperature hydrolysis reaction followed by seed-mediated growth. The nanoprobes render simultaneous dual functions of both fast magnetic response and local surface plasmon resonance. Using these nanoprobes, analyte molecules can be easily biologically captured, magnetically concentrated, and analyzed by surface-enhanced Raman scattering (SERS). Particularly, the complex particles were assembled under magnetic force direction into a SERS substrate. It was found to possess both a high enhancement factor (10(6)) and high homogeneity of "hot spot" distribution (fluctuation less than 20% for a 1 μm(2) area) with 4-aminothiophenol as the analyte.