Search results for "FREQUENCY"
showing 10 items of 2158 documents
Influence of the AC voltage frequency on the oscillation trajectory and path length of particles inside a planar–type electric curtain
2015
Abstract Experimental investigations of the average path length of oscillating dust particles inside a planar –type electric curtain (PTEC) are presented as a function of the frequency of the AC voltage. The frequency was adjusted within the range of 10–300 Hz. The oscillation paths of feldspar particles of diameter 40–60 μm inside a small cloud were recorded photographically. The main purpose of this investigation was to study the changes in average path length as a function of the supply voltage frequency. These results can be used to improve the precipitation and separation processes for charged dust particles inside a PTEC.
Dynamics of an active magnetic particle in a rotating magnetic field.
2006
The motion of an active (self-propelling) particle with a permanent magnetic moment under the action of a rotating magnetic field is considered. We show that below a critical frequency of the external field the trajectory of a particle is a circle. For frequencies slightly above the critical point the particle moves on an approximately circular trajectory and from time to time jumps to another region of space. Symmetry of the particle trajectory depends on the commensurability of the field period and the period of the orientational motion of the particle. We also show how our results can be used to study the properties of naturally occurring active magnetic particles, so-called magnetotacti…
3D motion of flexible ferromagnetic filaments under a rotating magnetic field.
2020
Ferromagnetic filaments in a rotating magnetic field are studied both numerically and experimentally. The filaments are made from micron-sized ferromagnetic particles linked with DNA strands. It is found that at low frequencies of the rotating field a filament rotates synchronously with the field and beyond a critical frequency it undergoes a transition to a three dimensional regime. In this regime the tips of the filament rotate synchronously with the field on circular trajectories in the plane parallel to the plane of the rotating field. The characteristics of this motion found numerically match the experimental data and allow us to obtain the physical properties of such filaments. We als…
246. Analysis of signal-to-noise ratio for a 2-channels coil developed to enable transcranial Magnetic Resonance-guided Focused Ultrasound Surgery (t…
2018
Abstract Purpose In recent years trans-cranial Magnetic Resonance-guided Focused Ultrasound Surgery (tcMRgFUS) treatments have aroused large scientific and medical interest [1] . Usually, tcMRgFUS systems are integrated with 3 T systems which allow the use of the body RF coil for both real time imaging and MR-thermometry. At University Hospital of Palermo there is the world-first installation of a tcMRgFUS system integrated with a 1.5 T scanner. Here we present the characterization in terms of signal-to-noise ratio (SNR) of a dedicated RF coils suitably developed (by InSightec) to enable tcMRgFUS treatments with 1.5 T MR units. Methods and materials The focused ultrasound equipment (ExAblat…
Absolute instability in backward wave four-wave mixing: spatial effects
2010
The spatial distribution of new beams generated above the threshold of absolute instability of two counterpropagating incoherent light waves is studied and compared with the results of calculation.
Extremely low frequency band station for natural electromagnetic noise measurement
2015
A new permanent ELF measurement station has been deployed in Sierra Nevada, Spain. It is composed of two magnetometers, oriented NS and EW, respectively. At 10 Hz, their sensitivity is 19 μV/pT and the signal-to-noise ratio (SNR) is 28 dB for a time-varying signal of 1 pT, the expected field amplitude in Sierra Nevada. The station operates for frequencies below 24 Hz. The magnetometers, together with their corresponding electronics, have been specifically designed to achieve such an SNR for small signals. They are based on high-resolution search coils with ferromagnetic core and 106 turns, operating in limited geometry configuration. Different system noise sources are considered, and a stud…
Evidence of electrical activity on Titan drawn from the Schumann resonances sent by Huygens probe
2008
Abstract A procedure is shown for extracting weak resonances from the responses of electromagnetic systems excited by electric discharges. The procedure, based on analysis of the late-time system response, is first checked using an analytical function and later with the data for the electric field generated by the computational simulation of Titan's atmosphere using the Transmission Line Matrix (TLM) method. Finally, the low frequency spectrum of the natural electric field in Titan's atmosphere sent by the mutual impedance sensor (MIP) included in the Huygens probe is analyzed employing this technique. The MIP sensor was initially designed to measure the horizontal component of the electric…
Epoch Parameterization by Gabor Atom Density in Experimental Epilepsy
2007
An Electrocorticogram (ECoG), during an epilepsy episode can change dramatically from the normal state into a high amplitude low frequency signal and suddenly return to the normal sate. It is possible to identify some stages in the epilepsy seizure, the most representative of them: basal, preictal, ictal and posictal. ECoG are highly non periodical signals, so they are analyze with T-F algorithms, in order to follow up its frequency evolution through the seizure stages. Each seizure stage has different frequency components and they show up at different time. Experimental epilepsy produce by kindling model in rats is used; signals are recorded at cortex level. The ECoG is decompose by means …
Photonically assisted RF generator with incoherent sources
2008
An RF waveform generator operating with incoherent broadband light is successfully implemented. Complex RF ~10 GHz bandwidth waveforms are generated by means of incoherent wavelength-to-time mapping. Our technique can be scaled to the mm-wave range.
Reconfigurable RF waveform generation using optical incoherent sources
2008
An RF waveform generator operating with incoherent broadband light is successfully implemented. Complex RF ~10 GHz bandwidth waveforms are generated by means of incoherent wavelength-to-time mapping. Our technique can be scaled to the mm-wave range.