Frequency Shift Parameters Research Articles

Realization of GPS Dynamic Hijacking Based on Software Radio

GPS positioning technology has a wide range of use scenarios, but due to the known characteristics of GPS signal open reception and modulation methods, many solutions can easily deceive GPS signals. Once this technology is abused in violation of regulations, it may cause major safety and property losses. In order to better study the anti-hijacking technology of PGS signals, this article starts with the generative dynamic hijacking of PGS, gives the implementation method based on software radio, and further learns the code phase and dopper between asynchronous hijacking and synchronous hijacking through software radio. The compensation calculation method of Leer frequency shift parameters, and verified the effect of the software radio’s GPS dynamic hijacking implementation method through examples, and provide theoretical support for the design and improvement of future anti-hijacking systems.

Fast Matching Pursuit with Multi-Gabor Dictionaries

Finding the best K -sparse approximation of a signal in a redundant dictionary is an NP-hard problem. Suboptimal greedy matching pursuit algorithms are generally used for this task. In this work, we present an acceleration technique and an implementation of the matching pursuit algorithm acting on a multi-Gabor dictionary, i.e., a concatenation of several Gabor-type time-frequency dictionaries, each of which consists of translations and modulations of a possibly different window and time and frequency shift parameters. The technique is based on pre-computing and thresholding inner products between atoms and on updating the residual directly in the coefficient domain, i.e., without the round-trip to the signal domain. Since the proposed acceleration technique involves an approximate update step, we provide theoretical and experimental results illustrating the convergence of the resulting algorithm. The implementation is written in C (compatible with C99 and C++11), and we also provide Matlab and GNU Octave interfaces. For some settings, the implementation is up to 70 times faster than the standard Matching Pursuit Toolkit.

Test and analysis of anti-seismic performance of recycled concrete on top of high-rise buildings

The anti-seismic performance of recycled concrete on top of high-rise buildings is influenced greatly by external environment. An analysis model for anti-seismic behavior of recycled concrete on top of high-rise buildings is proposed. The recycled concrete on top of high-rise buildings is divided into different layers, and anti-seismic signal at strong vibration signal of different level is separated to get the periodic characteristics variance of anti-seismic performance signal. Then, Doppler frequency shift parameters of the vibration signal are calculated to complete the anti-seismic performance test. The test results show that the anti-seismic performance of recycled concrete on top of high-rise buildings changes periodically.

Automatic Detection System And Method Of Spectral Doppler Blood Flow Velocity

A method and system for detecting spectral Doppler blood flow velocity are disclosed. The method comprises the steps of: obtaining Doppler signals of the flow by demodulating, filtering, and analog-to-digital converting RF ultrasonic echoes; analyzing the spectrum of the Doppler signals to obtain each of the power spectral lines of the Doppler signal varying with time; determining a threshold; and determining the frequency shift parameters or the blood flow velocity corresponding to the current power spectral line based on the threshold and the current power spectral line.

Equal energy phase space trajectories in resonant wave interactions

Adiabatic evolution of two and three resonantly interacting wave systems with nonlinear frequency/wave vector shifts is discussed. The corresponding Hamiltonian, depending on the coupling, detuning, and nonlinear frequency shift parameters may have a variable number of fixed points, i.e., the system can experience a topological change of phase space when these parameters vary in time or space. It is shown that the oscillation periods of two equal energy trajectories in these wave systems are equal and the difference between the action integrals of such trajectories is obtained analytically as a function of the system parameters. Based on these findings, a scheme of simultaneous adiabatic variation in the parameters is designed, such that any pair of initially equal energy trajectories continues to have the same energy at later times. These results are generalizations of a previous work [O. Polomarov and G. Shvets, Phys. Plasmas 13, 054502 (2006)] for a single, resonantly driven wave.

Measurement of permittivity and dielectric loss in 2,4-dimethyl substituted pyridine using microwave cavity spectrometer and time domain reflectometer

Microwave cavity spectrometer and time domain reflectometer is used to measure the permittivity and dielectric loss at different temperatures in 2,4-dimethyl substituted pyridine. The observed data of the width of resonance profile and the shift in the resonance frequency have been analyzed using Slater perturbation equations for cavity spectrometer. The dielectric parameters measured from the time domain reflectometer as a function of time at different temperatures have been transformed to frequency domain to obtain the permittivity and dielectric loss. The observed values of the permittivity and dielectric loss at 9.0 GHz are fitted in Slater's perturbation equations to obtain the form factor, which represents interactions. The relaxation time has been evaluated at different temperatures using the ratio of width and twice of frequency shift and thermodynamical parameters have been determined. This experimental study provides fruitful information about the bulk properties of 2,4-dimethyl substituted pyridine.

Note on B-splines, wavelet scaling functions, and gabor frames

Let g be a continuous, compactly supported function on such that the integer translates of g constitute a partition of unity. We show that the Gabor system (g,a,b), with window g and time-shift and frequency-shift parameters a,b>0 has no lower frame bound larger than 0 if b=2,3,... and a>0. In particular, (g,a,b) is not a Gabor frame if g is a continuous, compactly supported wavelet scaling function and if b=2,3,... and a>0. We give an example for our result for the case that g=B/sub 1/, the triangle function supported by [-1,1], by showing pictures of the canonical dual corresponding to (g,a,b) where ab=1/4 and b crosses the lines N=2,3,.

Discrepancies in experiments with cold hydrogen atoms

Recent experiments with atomic clocks and hydrogen gas samples have shown discrepancies between theory and experiment. There are serious disagreements with respect to four different parameters: two different frequency shift parameters and a line broadening cross section relating to the H maser, and a longitudinal relaxation rate observed in a hydrogen gas sample. We study the changes in the short-range singlet and triplet potentials that would be needed to eliminate the above discrepancies. We find that no such changes can remove all four discrepancies simultaneously. In addition, we investigate a possible role of spin-dipole interactions, which have been neglected in previous calculations.

Self-consistent dx2-y2 pairing in a two-dimensional Hubbard model.

Results of a conserving fluctuation exchange calculation for the superconducting state of a two-dimensional Hubbard model are presented. Self-consistent solutions for the full momentum- and frequency-dependent gap, renormalization, and frequency shift parameters have been obtained. The resulting frequency- and momentum-dependent gap is found to have ${\mathit{d}}_{\mathit{x}}^{2}$-${\mathit{y}}^{2}$ symmetry. Below ${\mathit{T}}_{\mathit{c}}$, the maximum gap opens rapidly to a low temperature 2\ensuremath{\Delta}(0)/${\mathit{kT}}_{\mathit{c}}$ value of order 10. We find that the effective interaction arising from the exchange of spin and charge fluctuations is stabilized by self-energy feedback effects as the superconducting gap opens.

Dependence of the oscillation frequency of a piezoelectric crystal on the physical parameters of liquids

A systematic comparative study was made of the oscillation behaviour of a piezoelectric quartz crystal immersed in various liquid systems of analytical interest including organic liquids, water/organic mixed solvents and aqueous solutions of various electrolytes, with a transistorized oscillator. The relationship between frequency shift and physical parameters of the liquids, and the effects of temperature and grounding are discussed.

Isotopic splitting in matrix isolated BF 3

Small isotopic frequency shift information, if precisely determined, provides an effective constraint on intramolecular force fields. The most precise data for these frequency shift parameters Δν are derived from high resolution, gas-phase infrared spectral analyses. In the present study, we compare for BF 3 the isotopic frequency shift Δν 4 from a recently published gas-phase study with the value for Δν 4 that we obtain from the spectrum of matrix isolated BF 3. The excellent agreement between the two methods suggests further applications of the matrix technique for obtaining precise frequency shift data.

Collision Broadening of Rotational Absorption Lines. I. Theoretical Formulation

An impact theory approach to the pressure broadening of microwave absorption lines is presented. A time-development matrix is evaluated to yield expressions which are averaged over all internal quantum states of the colliding molecule and the velocity distribution function to give half-width and frequency-shift parameters. The half-width parameter is then evaluated for dipole—dipole, dipole—quadrupole, quadrupole—quadrupole, and dispersion interactions. The dependence of the linewidths on the multipole moments, temperature, and the rotational state of the colliding molecule is discussed. The results are compared with previous theoretical treatments.