Study of the Method of Multi-Frequency Signal Detection Based on the Adaptive Stochastic Resonance
Directory of Open Access Journals (Sweden)
Zhenyu Lu
2013-01-01
Full Text Available Recently, the stochastic resonance effect has been widely used by the method of discovering and extracting weak periodic signals from strong noise through the stochastic resonance effect. The detection of the single-frequency weak signals by using stochastic resonance effect is widely used. However, the detection methods of the multifrequency weak signals need to be researched. According to the different frequency input signals of a given system, this paper puts forward a detection method of multifrequency signal by using adaptive stochastic resonance, which analyzed the frequency characteristics and the parallel number of the input signals, adjusted system parameters automatically to the low frequency signals in the fixed step size, and then measured the stochastic resonance phenomenon based on the frequency of the periodic signals to select the most appropriate indicators in the middle or high frequency. Finally, the optimized system parameters are founded and the frequency of the given signals is extracted in the frequency domain of the stochastic resonance output signals. Compared with the traditional detection methods, the method in this paper not only improves the work efficiency but also makes it more accurate by using the color noise, the frequency is more accurate being extracted from the measured signal. The consistency between the simulation results and analysis shows that this method is effective and feasible.
Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)
1995-01-01
A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.
Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)
1995-01-01
A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.
Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)
1995-01-01
A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.
Rajiv K Gupta; Thallam V Padmanabhan
2011-01-01
Initial stability at the placement and development of osseointegration are two major issues for implant survival. Implant stability is a mechanical phenomenon which is related to the local bone quality and quantity, type of implant, and placement technique used. The application of a simple, clinically applicable, non-invasive test to assess implant stability and osseointegration is considered highly desirable. Resonance frequency analysis (RFA) is one of such techniques which is most frequent...
Directory of Open Access Journals (Sweden)
Rajiv K Gupta
2011-01-01
Full Text Available Initial stability at the placement and development of osseointegration are two major issues for implant survival. Implant stability is a mechanical phenomenon which is related to the local bone quality and quantity, type of implant, and placement technique used. The application of a simple, clinically applicable, non-invasive test to assess implant stability and osseointegration is considered highly desirable. Resonance frequency analysis (RFA is one of such techniques which is most frequently used now days. The aim of this paper was to review and analyze critically the current available literature in the field of RFA, and to also discuss based on scientific evidence, the prognostic value of RFA to detect implants at risk of failure. A search was made using the PubMed database to find all the literature published on "Resonance frequency analysis for implant stability" till date. Articles discussed in vivo or in vitro studies comparing RFA with other methods of implant stability measurement and articles discussing its reliability were thoroughly reviewed and discussed. A limited number of clinical reports were found. Various studies have demonstrated the feasibility and predictability of the technique. However, most of these articles are based on retrospective data or uncontrolled cases. Randomized, prospective, parallel-armed longitudinal human trials are based on short-term results and long-term follow up are still scarce in this field. Nonetheless, from available literature, it may be concluded that RFA technique evaluates implant stability as a function of stiffness of the implant bone interface and is influenced by factors such as bone type, exposed implant height above the alveolar crest. Resonance frequency analysis could serve as a non-invasive diagnostic tool for detecting the implant stability of dental implants during the healing stages and in subsequent routine follow up care after treatment. Future studies, preferably randomized
Resonance and aspect matched adaptive radar (RAMAR)
Barrett, Terence William
2012-01-01
The book describes a new form of radar for which the target response is frequency, i.e., resonance-dependent. The book provides both prototype designs and empirical results collected from a variety of targets. The new form of radar, called RAMAR (Resonance and Aspect Matched Adaptive Radar) advances radar - mere ranging and detection - to the level of RF spectroscopy, and permits an advance of spectroscopic methods from optical, through infra-red and into the RF spectral range. The book will describe how a target's response can be a function of frequency components in the transmitted signal's
Acoustic resonance frequency locked photoacoustic spectrometer
Pilgrim, Jeffrey S.; Bomse, David S.; Silver, Joel A.
2003-09-09
A photoacoustic spectroscopy method and apparatus for maintaining an acoustic source frequency on a sample cell resonance frequency comprising: providing an acoustic source to the sample cell, the acoustic source having a source frequency; repeatedly and continuously sweeping the source frequency across the resonance frequency at a sweep rate; and employing an odd-harmonic of the source frequency sweep rate to maintain the source frequency sweep centered on the resonance frequency.
Ultra-high frequency magnetic resonance imaging
Magill, Arthur W.
2007-01-01
This thesis addresses the problem of radiofrequency probe design for Ultra High Frequency Magnetic Resonance Imaging (7T). The signal-to-noise ratio available in Magnetic Resonance Imaging (MRI) is determined by the static magnetic field strength, causing a continued drive toward higher fields to enable faster image acquisition at finer spatial resolution. The resonant frequency increases linearly with static field strength. At 7T the proton resonant frequency is 300MHz, with a wavelength...
Microwave Frequency Discriminator With Sapphire Resonator
Santiago, David G.; Dick, G. John
1994-01-01
Cooled sapphire resonator provides ultralow phase noise. Apparatus comprises microwave oscillator operating at nominal frequency of about 8.1 GHz, plus frequency-discriminator circuit measuring phase fluctuations of oscillator output. One outstanding feature of frequency discriminator is sapphire resonator serving as phase reference. Sapphire resonator is dielectric ring resonator operating in "whispering-gallery" mode. Functions at room temperature, but for better performance, typically cooled to operating temperature of about 80 K. Similar resonator described in "Sapphire Ring Resonator for Microwave Oscillator" (NPO-18082).
Magnetic Earth Ionosphere Resonant Frequencies
Spaniol, Craig
1994-01-01
The Community College Division is pleased to report progress of NASA funded research at West Virginia State College. During this reporting period, the project research group has continued with activities to develop instrumentation capability designed to monitor resonant cavity frequencies in the atmospheric region between the Earth's surface and the ionosphere. In addition, the project's principal investigator, Dr. Craig Spaniol, and NASA technical officer, Dr. John Sutton, have written and published technical papers intended to expand the scientific and technical framework needed for project research. This research continues to provide an excellent example of government and education working together to provide significant research in the college environment. This cooperative effort has provided many students with technical project work which compliments their education.
Resonance frequency in respiratory distress syndrome
Lee, S.; Milner, A
2000-01-01
AIM—To observe how the resonance frequency changes with the course of respiratory distress syndrome (RDS), by examining the effect of changing static compliance on the resonance frequency in premature infants. METHODS—In 12 ventilated premature infants with RDS (mean gestational age 26.6 weeks, mean birth weight 0.84 kg), resonance frequency and static compliance were determined serially using phase analysis and single breath mechanics technique respectively in the first ...
Resonant frequencies of whispering gallery modes of dielectric resonator
S.L. Badnilcar; N.Shanmugam; V. R. K. Murthy
2001-01-01
The modal spectrum of the whispering gallery modes of dielectric resonator depends mainly on its physical dimensions, dielectric constant, and to a lesser extent, on the environment. This paper carries investigation of the resonant frequencies in dielectric disc utilising the ring resonator model. Results of the structural design parameters are used to generate a nume!ical expression for describing the operational frequencies useful for computer-aided design applications. Theoretical ...
Novel resonant cantilever mass change detection and resonant frequency tuning
DEFF Research Database (Denmark)
Grigorov, Alexander; Boisen, Anja
2005-01-01
structure due to mass changes. Thus the device can only be used once and is best suited for qualitative mass detection. At the same time, the resonant frequency of the device can be tuned by the input signal power. This allows scanning power instead of frequency, and simplifies device operation......This paper reports a novel way to detect the resonant frequency of an electro-thermally actuated cantilever sensor that we have previously reported, in order to perform mass detection by resonant frequency shift detection. The device is based on monitoring the rupture of a clamped cantilever...
Feshbach Resonances in Kerr Frequency Combs
Matsko, Andrey B
2014-01-01
We show that both the power and repetition rate of a frequency comb generated in a nonlinear ring resonator, pumped with continuous wave (cw) coherent light, are modulated. The modulation is brought about by the interaction of the cw background with optical pulses excited in the resonator, and occurs in resonators with nonzero high-order chromatic dispersion and wavelength-dependent quality factor. The modulation frequency corresponds to the detuning of the pump frequency from the eigenfrequency of the pumped mode in the resonator.
High Energy Single Frequency Resonant Amplifier Project
National Aeronautics and Space Administration — This SBIR phase I project proposes a single frequency high energy resonant amplifier for remote sensing. Current state-of-art technologies can not provide all...
On Frequency Combs in Monolithic Resonators
Directory of Open Access Journals (Sweden)
Savchenkov A. A.
2016-06-01
Full Text Available Optical frequency combs have become indispensable in astronomical measurements, biological fingerprinting, optical metrology, and radio frequency photonic signal generation. Recently demonstrated microring resonator-based Kerr frequency combs point the way towards chip scale optical frequency comb generator retaining major properties of the lab scale devices. This technique is promising for integrated miniature radiofrequency and microwave sources, atomic clocks, optical references and femtosecond pulse generators. Here we present Kerr frequency comb development in a historical perspective emphasizing its similarities and differences with other physical phenomena. We elucidate fundamental principles and describe practical implementations of Kerr comb oscillators, highlighting associated solved and unsolved problems.
Rod Driven Frequency Entrainment and Resonance Phenomena
Directory of Open Access Journals (Sweden)
Christina Salchow
2016-08-01
Full Text Available A controversy exists on photic driving in the human visual cortex evoked by intermittent photic stimulation. Frequency entrainment and resonance phenomena are reported for frequencies higher than 12 Hz in some studies while missing in others. We hypothesized that this might be due to different experimental conditions, since both high and low intensity light stimulation were used. However, most studies do not report radiometric measurements, which makes it impossible to categorize the stimulation according to photopic, mesopic, and scotopic vision. Low intensity light stimulation might lead to scotopic vision, where rod perception dominates. In this study, we investigated photic driving for rod-dominated visual input under scotopic conditions. Twelve healthy volunteers were stimulated with low intensity light flashes at 20 stimulation frequencies, leading to rod activation only. The frequencies were multiples of the individual alpha frequency (α of each volunteer in the range from 0.40–2.30*α. 306-channel whole head magnetoencephalography recordings were analyzed in time, frequency, and spatiotemporal domains with the Topographic Matching Pursuit algorithm. We found resonance phenomena and frequency entrainment for stimulations at or close to the individual alpha frequency (0.90–1.10*α and half of the alpha frequency (0.40–0.55*α. No signs of resonance and frequency entrainment phenomena were revealed around 2.00*α. Instead, on-responses at the beginning and off-responses at the end of each stimulation train were observed for the first time in a photic driving experiment at frequencies of 1.30–2.30*α, indicating that the flicker fusion threshold was reached. All results, the resonance and entrainment as well as the fusion effects, provide evidence for rod-dominated photic driving in the visual cortex.
Rod Driven Frequency Entrainment and Resonance Phenomena
Salchow, Christina; Strohmeier, Daniel; Klee, Sascha; Jannek, Dunja; Schiecke, Karin; Witte, Herbert; Nehorai, Arye; Haueisen, Jens
2016-01-01
A controversy exists on photic driving in the human visual cortex evoked by intermittent photic stimulation. Frequency entrainment and resonance phenomena are reported for frequencies higher than 12 Hz in some studies while missing in others. We hypothesized that this might be due to different experimental conditions, since both high and low intensity light stimulation were used. However, most studies do not report radiometric measurements, which makes it impossible to categorize the stimulation according to photopic, mesopic, and scotopic vision. Low intensity light stimulation might lead to scotopic vision, where rod perception dominates. In this study, we investigated photic driving for rod-dominated visual input under scotopic conditions. Twelve healthy volunteers were stimulated with low intensity light flashes at 20 stimulation frequencies, leading to rod activation only. The frequencies were multiples of the individual alpha frequency (α) of each volunteer in the range from 0.40 to 2.30∗α. Three hundred and six-channel whole head magnetoencephalography recordings were analyzed in time, frequency, and spatiotemporal domains with the Topographic Matching Pursuit algorithm. We found resonance phenomena and frequency entrainment for stimulations at or close to the individual alpha frequency (0.90–1.10∗α) and half of the alpha frequency (0.40–0.55∗α). No signs of resonance and frequency entrainment phenomena were revealed around 2.00∗α. Instead, on-responses at the beginning and off-responses at the end of each stimulation train were observed for the first time in a photic driving experiment at frequencies of 1.30–2.30∗α, indicating that the flicker fusion threshold was reached. All results, the resonance and entrainment as well as the fusion effects, provide evidence for rod-dominated photic driving in the visual cortex. PMID:27588002
Study on resonance frequency of thermoacoustic resonance pipes
Institute of Scientific and Technical Information of China (English)
FAN Li; WANG Benren; JIN Tao; ZHANG Shuyi
2005-01-01
For calculating the resonance frequency of practical resonance pipes more precisely, two methods are presented, which are the method of acoustic pressure simulation and the method of minimum point of standing wave. Both methods are based on the theoretical simulation of the acoustic pressure distribution in the pipe and the relation between the minimum point position of the standing wave and the acoustic impedances of the pipe terminations.It is demonstrated that both methods can calculate the resonance frequency of a pipe more precisely by considering the effect of the acoustic resistances of both terminations of the pipe.Therefore both methods presented are more useful in acoustic research fields in which the resonance frequency of a pipe must be controlled strictly. In addition, both methods can get the same calculation results despite of their different ways. The method of the minimum point of standing wave is more convenient, nevertheless the method of acoustic pressure simulation can derive the resonance frequency and the distribution of the acoustic pressure in the pipe simultaneously.
Frequency shifts in gravitational resonance spectroscopy
Baeßler, S; Pignol, G; Protasov, K V; Rebreyend, D; Kupriyanova, E A; Voronin, A Yu
2015-01-01
Quantum states of ultracold neutrons in the gravitational field are to be characterized through gravitational resonance spectroscopy. This paper discusses systematic effects that appear in the spectroscopic measurements. The discussed frequency shifts, which we call Stern-Gerlach shift, interference shift, and spectator state shift, appear in conceivable measurement schemes and have general importance. These shifts have to be taken into account in precision experiments.
Optical ballast and adaptive dynamic stable resonator
Institute of Scientific and Technical Information of China (English)
Zhang Guang-Yin; Jiao Zhi-Yong; Guo Shu-Guang; Zhang Xiao-Hua; Gu Xue-Wen; Yan Cai-Fan; Wu Ding-Er; Song Feng
2004-01-01
In this paper a new concept of ‘optical ballast' is put forward. Optical ballast is a kind of device that can be used to decrease the variation and fluctuation of the propagation characteristics of light beams caused by the disturbance of refractive index of the medium. To illustrate the idea clearly and concretely, a fully adaptive dynamic stable solid-state laser resonator is presented as application example of optical ballast.
Andersen, Christian Kraglund; Mølmer, Klaus
2015-03-01
A SQUID inserted in a superconducting waveguide resonator imposes current and voltage boundary conditions that makes it suitable as a tuning element for the resonator modes. If such a SQUID element is subject to a periodically varying magnetic flux, the resonator modes acquire frequency side bands. We calculate the multi-frequency eigenmodes and these can couple resonantly to physical systems with different transition frequencies and this makes the resonator an efficient quantum bus for state transfer and coherent quantum operations in hybrid quantum systems. As an example of the application, we determine their coupling to transmon qubits with different frequencies and we present a bi-chromatic scheme for entanglement and gate operations. In this calculation, we obtain a maximally entangled state with a fidelity F = 95 % . Our proposal is competitive with the achievements of other entanglement-gates with superconducting devices and it may offer some advantages: (i) There is no need for additional control lines and dephasing associated with the conventional frequency tuning of qubits. (ii) When our qubits are idle, they are far detuned with respect to each other and to the resonator, and hence they are immune to cross talk and Purcell-enhanced decay.
Wen-Yu Wang; An-Wen Shen
2012-01-01
A novel method for middle frequency resonance detection and reduction is proposed for speed control in industrial servo systems. Defects of traditional resonance reduction method based on adaptive notch filter in middle frequency range are analyzed. And the main reason is summarized as the difference between the resonance frequency and the oscillation frequency. A self-tuning low-pass filter is introduced in the speed feedback path, whose corner frequency is determined by FFT results and seve...
Adaptive contrast imaging: transmit frequency optimization
Ménigot, Sébastien; Novell, Anthony; Voicu, Iulian; Bouakaz, Ayache; Girault, Jean-Marc
2010-01-01
Introduction: Since the introduction of ultrasound (US) contrast imaging, the imaging systems use a fixed emitting frequency. However it is known that the insonified medium is time-varying and therefore an adapted time-varying excitation is expected. We suggest an adaptive imaging technique which selects the optimal transmit frequency that maximizes the acoustic contrast. Two algorithms have been proposed to find an US excitation for which the frequency was optimal with microbubbles. Methods and Materials: Simulations were carried out for encapsulated microbubbles of 2 microns by considering the modified Rayleigh-Plesset equation for 2 MHz transmit frequency and for various pressure levels (20 kPa up to 420kPa). In vitro experiments were carried out using a transducer operating at 2 MHz and using a programmable waveform generator. Contrast agent was then injected into a small container filled with water. Results and discussions: We show through simulations and in vitro experiments that our adaptive imaging technique gives: 1) in case of simulations, a gain of acoustic contrast which can reach 9 dB compared to the traditional technique without optimization and 2) for in vitro experiments, a gain which can reach 18 dB. There is a non negligible discrepancy between simulations and experiments. These differences are certainly due to the fact that our simulations do not take into account the diffraction and nonlinear propagation effects. Further optimizations are underway.
Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) project
Spaniol, Craig
1993-01-01
The West Virginia State College Community College Division NASA Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) study is described. During this contract period, the two most significant and professionally rewarding events were the presentation of the research activity at the Sir Isaac Newton Conference in St. Petersburg, Russia, and the second Day of Discovery Conference, focusing on economic recovery in West Virginia. An active antenna concept utilizing a signal feedback principle similar to regenerative receivers used in early radio was studied. The device has potential for ELF research and other commercial applications for improved signal reception. Finally, work continues to progress on the development of a prototype monitoring station. Signal monitoring, data display, and data storage are major areas of activity. In addition, we plan to continue our dissemination of research activity through presentations at seminars and other universities.
Study on resonance frequency distribution of high-overtone bulk acoustic resonators
Institute of Scientific and Technical Information of China (English)
ZHANG Hui; WANG Zuoqing; ZHANG Shuyi
2005-01-01
Based on the method of characterizing piezo-films by the resonance frequency distributions, the factors influencing the resonance frequency distribution of a High-overtone Bulk Acoustic Resonator (HBAR) consisting of a piezoelectric thin film with twoelectrodes and a substrate are studied. Some HBARs are simulated. The results manifest that changing the acoustic impedance ratio of the substrate to piezo-film the distribution of the space of the parallel resonance frequency and the effective electromechanical coupling factor are changed. When the fundamental mode of the piezo-film is at high frequency, changing the acoustic impedance ratio of the electrode to piezo-film and the thickness of the electrodes make the resonance frequency distribution of HBARs change. These results manifest that the HBARs can be resonant at specified frequencies by means of adjusting the factors affecting the resonance frequency distribution.
RCCS operation with a resonant frequency error in the KOMAC
Seo, Dong-Hyuk
2015-10-01
The resonance control cooling systems (RCCSs) of the Korea Multi-purpose Accelerator Complex have been operated for cooling the drift tubes (DT) and controlling the resonant frequency of the drift tube linac (DTL). The DTL should maintain a resonant frequency of 350 MHz during operation. A RCCS can control the temperature of the cooling water to within ±0.1 °C by using a 3-way valve opening and has a constant-cooling-water-temperature control mode and resonant-frequency-control mode. In the case of the resonant-frequency control, the error in the frequency is measured by using the low-level radio-frequency control system, and the RCCS uses a proportional-integral-derivative control algorithm to compensate for the error by controlling the temperature of the cooling water to the DT.
Mixed frequency excitation of an electrostatically actuated resonator
Ramini, Abdallah
2015-04-24
We investigate experimentally and theoretically the dynamics of a capacitive resonator under mixed frequency excitation of two AC harmonic signals. The resonator is composed of a proof mass suspended by two cantilever beams. Experimental measurements are conducted using a laser Doppler vibrometer to reveal the interesting dynamics of the system when subjected to two-source excitation. A nonlinear single-degree-of-freedom model is used for the theoretical investigation. The results reveal combination resonances of additive and subtractive type, which are shown to be promising to increase the bandwidth of the resonator near primary resonance frequency. Our results also demonstrate the ability to shift the combination resonances to much lower or much higher frequency ranges. We also demonstrate the dynamic pull-in instability under mixed frequency excitation. © 2015 Springer-Verlag Berlin Heidelberg
Variable frequency iteration MPPT for resonant power converters
Energy Technology Data Exchange (ETDEWEB)
Zhang, Qian; Bataresh, Issa; Chen, Lin
2015-06-30
A method of maximum power point tracking (MPPT) uses an MPPT algorithm to determine a switching frequency for a resonant power converter, including initializing by setting an initial boundary frequency range that is divided into initial frequency sub-ranges bounded by initial frequencies including an initial center frequency and first and second initial bounding frequencies. A first iteration includes measuring initial powers at the initial frequencies to determine a maximum power initial frequency that is used to set a first reduced frequency search range centered or bounded by the maximum power initial frequency including at least a first additional bounding frequency. A second iteration includes calculating first and second center frequencies by averaging adjacent frequent values in the first reduced frequency search range and measuring second power values at the first and second center frequencies. The switching frequency is determined from measured power values including the second power values.
Directory of Open Access Journals (Sweden)
Wen-Yu Wang
2012-01-01
Full Text Available A novel method for middle frequency resonance detection and reduction is proposed for speed control in industrial servo systems. Defects of traditional resonance reduction method based on adaptive notch filter in middle frequency range are analyzed. And the main reason is summarized as the difference between the resonance frequency and the oscillation frequency. A self-tuning low-pass filter is introduced in the speed feedback path, whose corner frequency is determined by FFT results and several self-tuning rules. With the proposed method the effective range of the adaptive filter is extended across the middle frequency range. Simulation and Experiment results show that the frequency detection is accurate and resonances during the speed steady states and dynamics are successfully reduced.
Resonant difference-frequency atomic force ultrasonic microscope
Cantrell, John H. (Inventor); Cantrell, Sean A. (Inventor)
2010-01-01
A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.
Low Frequency Scattering Resonance Wave in Strong Heterogeneity
Liu, Yinbin
2015-01-01
Multiple scattering of wave in strong heterogeneity can cause resonance-like wave phenomenon where signal exhibits low frequency, high intensity, and slowly propagating velocity. For example, long period event in volcanic seismology and surface plasmon wave and quantum Hall effect in wave-particle interactions. Collective behaviour in a many-body system is usually thought to be the source for generating the anomaly. However, the detail physical mechanism is not fully understood. Here I show by wave field modeling for microscopic bubble cloud model and 1D heterogeneity that the anomaly is related to low frequency scattering resonance happened in transient regime. This low frequency resonance is a kind of wave coherent scattering enhancement phenomenon in strongly-scattered small-scale heterogeneity. Its resonance frequency is inversely proportional to heterogeneous scale and contrast and will further shift toward lower frequency with random heterogeneous scale and velocity fluctuations. Low frequency scatterin...
Adaptive Helmholtz resonators and passive vibration absorbers for cylinder interior noise control
Estève, Simon J.; Johnson, Marty E.
2005-12-01
This paper presents an adaptive-passive solution to control the broadband sound transmission into rocket payload fairings. The treatment is composed of passive distributed vibration absorbers (DVAs) and adaptive Helmholtz resonators (HR). Both the frequency domain and time-domain model of a simply supported cylinder excited by an external plane wave are developed. To tune vibration absorbers to tonal excitation, a tuning strategy, based on the phase information between the velocity of the absorber mass and the velocity of the host structure is used here in a new fashion to tune resonators to peaks in the broadband acoustic spectrum of a cavity. This tuning law, called the dot-product method, only uses two microphone signals local to each HR, which allows the adaptive Helmholtz resonator (AHR) to be manufactured as an autonomous device with power supply, sensor, actuator and controller integrated. Numerical simulations corresponding to a 2.8 m long 2.5 m diameter composite cylinder prototype demonstrate that, as long as the structure modes, which strongly couple to the acoustic cavity, are damped with a DVA treatment, the dot-product method tune multiple HRs to a near-optimal solution over a broad frequency range (40-160 Hz). An adaptive HR prototype with variable opening is built and characterized. Experiments conducted on the cylinder prototype with eight AHRs demonstrate the ability of resonators adapted with the dot-product method to converge to near-optimal noise attenuation in a frequency band including multiple resonances.
A Quarter Ellipse Microstrip Resonator for Filters in Microwave Frequencies
Directory of Open Access Journals (Sweden)
Samuel Á. Jaramillo-Flórez
2013-11-01
Full Text Available This work describes the results of computational simulations and construction of quadrant elliptical resonators excited by coplanar slot line waveguide for designing microwave filters in RF communications systems. By means of the equation of optics, are explained the fundamentals of these geometry of resonators proposed. Are described the construction of quadrant elliptical resonators, one of microstrip and other two of cavity, of size different, and an array of four quadrant elliptical resonators in cascade. The results of the measures and the computational calculus of scattering S11 and S21 of elliptical resonators is made for to identify the resonant frequencies of the resonators studied, proving that these have performance in frequency as complete ellipses by the image effect due to their two mirror in both semiaxis, occupying less area, and the possible applications are discussed.
Tunable characteristics of bending resonance frequency in magnetoelectric laminated composites
Chen, Lei; Li, Ping; Wen, Yu-Mei; Zhu, Yong
2013-07-01
As the magnetoelectric (ME) effect in piezoelectric/magnetostrictive laminated composites is mediated by mechanical deformation, the ME effect is significantly enhanced in the vicinity of resonance frequency. The bending resonance frequency (fr) of bilayered Terfenol-D/PZT (MP) laminated composites is studied, and our analysis predicts that (i) the bending resonance frequency of an MP laminated composite can be tuned by an applied dc magnetic bias (Hdc) due to the ΔE effect; (ii) the bending resonance frequency of the MP laminated composite can be controlled by incorporating FeCuNbSiB layers with different thicknesses. The experimental results show that with Hdc increasing from 0 Oe (1 Oe=79.5775 A/m) to 700 Oe, the bending resonance frequency can be shifted in a range of 32.68 kHz bending resonance frequency of the MP laminated composite gradually increases from 33.66 kHz to 39.18 kHz. This study offers a method of adjusting the strength of dc magnetic bias or the thicknesses of the FeCuNbSiB layer to tune the bending resonance frequency for ME composite, which plays a guiding role in the ME composite design for real applications.
Tunable characteristics of bending resonance frequency in magnetoelectric laminated composites
Institute of Scientific and Technical Information of China (English)
Chen Lei; Li Ping; Wen Yu-Mei; Zhu Yong
2013-01-01
As the magnetoelectric (ME) effect in piezoelectric/magnetostrictive laminated composites is mediated by mechanical deformation,the ME effect is significantly enhanced in the vicinity of resonance frequency.The bending resonance frequency (fr) of bilayered Terfenol-D/PZT (MP) laminated composites is studied,and our analysis predicts that (i) the bending resonance frequency of an MP laminated composite can be tuned by an applied dc magnetic bias (Hdc) due to the △E effect; (ii) the bending resonance frequency of the MP laminated composite can be controlled by incorporating FeCuNbSiB layers with different thicknesses.The experimental results show that with Hdc increasing from 0Oe (1 Oe=79.5775 A/m)to 700 Oe,the bending resonance frequency can be shifted in a range of 32.68 kHz ≤ fr ≤ 33.96 kHz.In addition,with the thickness of the FeCuNbSiB layer increasing from 0 μm to 90 μm,the bending resonance frequency of the MP laminated composite gradually increases from 33.66 kHz to 39.18 kHz.This study offers a method of adjusting the strength of dc magnetic bias or the thicknesses of the FeCuNbSiB layer to tune the bending resonance frequency for ME composite,which plays a guiding role in the ME composite design for real applications.
Resonance enhancement by suitably chosen frequency detuning
Dutykh, Denys
2014-01-01
In this Letter we report new effects of resonance detuning on various dynamical parameters of a generic 3-wave system. Namely, for suitably chosen values of detuning the variation range of amplitudes can be significantly wider than for exact resonance. Moreover, the range of energy variation is not symmetric with respect to the sign of the detuning. Finally, the period of the energy oscillation exhibits non-monotonic dependency on the magnitude of detuning. These results have important theoretical implications where nonlinear resonance analysis is involved, such as geophysics, plasma physics, fluid dynamics. Numerous practical applications are envisageable e.g. in energy harvesting systems.
ANALYSIS OF PIEZOELECTRIC ENERGY HARVESTING DEVICE WITH ADJUSTABLE RESONANCE FREQUENCY
Institute of Scientific and Technical Information of China (English)
Jiang Lei; Li Yuejuan; Marvin Cheng
2012-01-01
This paper presents an analytic method that adjusts resonance frequency of a piezoelectric vibration energy harvester.A mathematical model that estimates resonance frequency of cantilever is also proposed.Through moving an attached mass and changing its weight on the cantilever beam,resonance frequency of adopted piezoelectric device can be adjusted to match the frequency of ambient vibration sources,which is critical in order to harvest maximum amount of energy.The theoretical results are validated by experiments that move different masses along experimental cantilever beams.The results demonstrate that resonance frequency can be adjusted by an attached mass located at different positions on the cantilever beam.Different combinations of operational conditions that harvest maximum amount of energy are also discussed in this paper.
Memory recall and spike-frequency adaptation
Roach, James P.; Sander, Leonard M.; Zochowski, Michal R.
2016-05-01
The brain can reproduce memories from partial data; this ability is critical for memory recall. The process of memory recall has been studied using autoassociative networks such as the Hopfield model. This kind of model reliably converges to stored patterns that contain the memory. However, it is unclear how the behavior is controlled by the brain so that after convergence to one configuration, it can proceed with recognition of another one. In the Hopfield model, this happens only through unrealistic changes of an effective global temperature that destabilizes all stored configurations. Here we show that spike-frequency adaptation (SFA), a common mechanism affecting neuron activation in the brain, can provide state-dependent control of pattern retrieval. We demonstrate this in a Hopfield network modified to include SFA, and also in a model network of biophysical neurons. In both cases, SFA allows for selective stabilization of attractors with different basins of attraction, and also for temporal dynamics of attractor switching that is not possible in standard autoassociative schemes. The dynamics of our models give a plausible account of different sorts of memory retrieval.
Multi-resonance split ring resonator structures at sub-terahertz frequencies
Galal, Hossam
2016-01-01
This paper reports on the computational development of novel architectures of multi-resonance Split Ring Resonators (SRRs), for efficient manipulation of Terahertz (THz) frequency beams. The conceived resonators are based on both a capacitive and inductive scheme. Simulation results have been obtained for a 60 GHz to 240 GHz operational bandwidth.
Phase-Shift Control of Resonant Frequencies of Magnetostatic Wave Resonators
Koike, Takuro; Nakazawa, Hiroaki
1994-05-01
We discuss a possible technique to control the resonant frequencies of a straight-edge magnetostatic wave (MSW) resonator without changing the external applied magnetic field and the circuit parameters of a feedback load circuit. The method is to use two additional microstrip electrodes at the edges of the resonator and two varactor diodes connected in series. Upon varying the bias voltages to the varactor diodes, the input admittance at the center electrode can be changed. Theoretical investigation reveals that very large resonant frequency shifts can be obtained by changing only the bias voltage change to the varactor diodes, which may be useful in mobile telephone applications in the gigaherz frequency range.
Stochastic resonance in two-frequency signal systems
Song, Hui; Huang, Shengming; Liu, Xuemei
2016-04-01
Signal-to-noise ratio (SNR) in two-frequency signal systems is investigated in the presence of the correlated multiplicative and white additive noises. From the Wiener-Khinchin theorem, the exact expression of the SNR is obtained. It is found that stochastic resonance (SR) appears when two frequencies are almost the same, while SR gradually disappears when the frequency difference increases. We also found that there exists an optimized value of the frequency at which SNR takes its maximal value.
Generation of Kerr Frequency Combs in Resonators with Normal GVD
Matsko, Andrey B; Maleki, Lute
2011-01-01
We show via numerical simulation that Kerr frequency combs can be generated in a nonlinear resonator characterized with normal group velocity dispersion (GVD). We find the spectral shape of the comb and temporal envelope of the corresponding optical pulses formed in the resonator.
Low frequency wave resonance in fringing reef environments
Pomeroy, A.W.M.; van Dongeren, A.; Lowe, R.J.; Van Thiel de Vries, J.S.M.; Roelvink, J.A.
2012-01-01
Low frequency wave resonance has been postulated to enhance damage to coral reef protected coastlines during storm events. This paper uses the numerical model XBeach to examine the dynamics that contribute to resonance that have been previously observed on a fringing reef on Guam during tropical sto
Planar terahertz metamaterial with three-resonant frequencies
Institute of Scientific and Technical Information of China (English)
Chen Zhi; Zhang Ya-Xin
2013-01-01
In this paper,we study a three-resonant metamaterial with the combination of dual-resonant and single-resonant metamaterials.We present a new method to design multi-resonant metamaterial,which has a smaller dimension than general symmetric and asymmetric multi-resonant metamaterials.Theoretical and experimental results show that the structure has three distinct absorption frequencies centering around 0.29 THz,0.46 THz,and 0.92 THz,and that each of them corresponds to a different resonant mode.Due to the good separation of the different resonances,this design provides a unique and effective method to construct multiband terahertz devices.
Chemisorption-Induced Resonance Frequency Shift of a Microcantilever
International Nuclear Information System (INIS)
The autonomy and property of atoms/molecules adsorbed on the surface of a microcantilever can be probed by measuring its resonance frequency shift due to adsorption. The resonance frequency change of a cantilever induced by chemisorption is theoretically studied. Oxygen chemisorbed on the Si(100) surface is taken as a representative example. We demonstrate that the resonant response of the cantilever is mainly determined by the chemisorption-induced bending stiffness variation, which depends on the bond configurations formed by the adsorbed atoms and substrate atoms. This study is helpful for optimal design of microcantilever-based sensors for various applications. (condensed matter: structure, mechanical and thermal properties)
Micro--structured crystalline resonators for optical frequency comb generation
Grudinin, Ivan S
2014-01-01
Optical frequency combs have recently been demonstrated in micro--resonators through nonlinear Kerr processes. Investigations in the past few years provided better understanding of micro--combs and showed that spectral span and mode locking are governed by cavity spectrum and dispersion. While various cavities provide unique advantages, dispersion engineering has been reported only for planar waveguides. In this Letter, we report a resonator design that combines dispersion control, mode crossing free spectrum, and ultra--high quality factor. We experimentally show that as the dispersion of a MgF2 resonator is flattened, the comb span increases reaching 700 nm with as low as 60 mW pump power at 1560 nm wavelength, corresponding to nearly 2000 lines separated by 46 GHz. The new resonator design may enable efficient low repetition rate coherent octave spanning frequency combs without the need for external broadening, ideal for applications in optical frequency synthesis, metrology, spectroscopy, and communicatio...
Frequency Noise in Superconducting Thin-Film Resonators
Kumar, Shwetank; Day, Peter; Leduc, Henry; Mazin, Benjamin; Eckart, Megan; Gao, Jiansong; Zmuidzinas, Jonas
2006-03-01
We present the results of low temperature (120 -- 1200 mK) noise measurements performed on thin-film superconducting niobium resonators fabricated on a silicon substrate. The devices studied use coplanar waveguide (CPW) transmission lines and have resonance frequencies of around 4 GHz and quality factors in the range of Q ˜ 10^4 to 10^6. These resonators are similar to those used to make novel photon detectors and read out charge qubits. These resonators show excess frequency noise which varies as approximately f-1/2. This excess noise limits the sensitivity of our photon detectors and likely effects the qubit performance as well. Two level systems (TLS) in amorphous thin-film dielectrics and oxide tunnel barriers have been shown to cause dissipation and decoherence in phase qubits. We suggest that noise in our resonators is also caused by TLS most likely near the surfaces of the substrate and metal films. To test this idea, we have measured the frequency shift, the quality factor and the frequency noise as a function of the device temperature and the microwave readout power. The frequency shift data agrees well with existing weak field TLS theory. We also find that the frequency noise decreases with increasing readout power and temperature and that decreased noise at higher powers is not due to simply device heating.
Resonances in low frequency ionization by periodic electric fields
Energy Technology Data Exchange (ETDEWEB)
Dando, P.A.; Richards, D. (Open Univ., Milton Keynes (United Kingdom). Mathematics Faculty)
1993-09-28
The behaviour of a one-dimensional system perturbed by a low frequency, periodic electric field is examined in the limit as the field frequency, [Omega], tends to zero, that is the static field limit. In particular we obtain estimates of the widths of each member of the infinite set of resonances between any finite value of [Omega] and 0. In order to obtain this estimate we derive a new analytic approximation of the two-state equations of motion. Our analysis shows why recent experiments on the ionization of excited hydrogen atoms by low frequency fields failed to observe any resonances. (author).
Squeezing Alters Frequency Tuning of WGM Optical Resonator
Mohageg, Makan; Maleki, Lute
2010-01-01
Mechanical squeezing has been found to alter the frequency tuning of a whispering-gallery-mode (WGM) optical resonator that has an elliptical shape and is made of lithium niobate. It may be possible to exploit this effect to design reconfigurable optical filters for optical communications and for scientific experiments involving quantum electrodynamics. Some background information is prerequisite to a meaningful description of the squeezing-induced alteration of frequency tuning: The spectrum of a WGM resonator is represented by a comblike plot of intensity versus frequency. Each peak of the comblike plot corresponds to an electromagnetic mode represented by an integer mode number, and the modes are grouped into sets represented by integer mode indices. Because lithium niobate is an electro-optically active material, the WGM resonator can be tuned (that is, the resonance frequencies can be shifted) by applying a suitable bias potential. The frequency shift of each mode is quantified by a tuning rate defined as the ratio between the frequency shift and the applied potential. In the absence of squeezing, all modes exhibit the same tuning rate. This concludes the background information. It has been demonstrated experimentally that when the resonator is squeezed along part of either of its two principal axes, tuning rates differ among the groups of modes represented by different indices (see figure). The differences in tuning rates could be utilized to configure the resonance spectrum to obtain a desired effect; for example, through a combination of squeezing and electrical biasing, two resonances represented by different mode indices could be set at a specified frequency difference something that could not be done through electrical biasing alone.
Directory of Open Access Journals (Sweden)
Hilmi Volkan Demir
2009-11-01
Full Text Available We present circular architecture bioimplant strain sensors that facilitate a strong resonance frequency shift with mechanical deformation. The clinical application area of these sensors is for in vivo assessment of bone fractures. Using a rectangular geometry, we obtain a resonance shift of 330 MHz for a single device and 170 MHz for its triplet configuration (with three side-by-side resonators on chip under an applied load of 3,920 N. Using the same device parameters with a circular isotropic architecture, we achieve a resonance frequency shift of 500 MHz for the single device and 260 MHz for its triplet configuration, demonstrating substantially increased sensitivity.
Resonance Micro-Weighing of Sub-Picogram Mass with the Use of Adaptive Interferometer
Directory of Open Access Journals (Sweden)
Romashko Roman
2014-06-01
Full Text Available Mass of macroscopic object is easily measured by a suitable balance. However, this approach becomes inapplicable if mass of microscopic object is to be determined. Alternative approach for mass measurement is based on using the micromechanical resonator as an inertial balance where oscillation frequency is shifted by small quantities of adsorbed mass. In this work we present experimental results of applying an adaptive interferometry technique based on dynamic hologram recorded in photorefractive CdTe crystal for measuring picogram mass adsorbed on micromechanical resonators with dimensions 215×40×15 μm3. It is also shown that the resonance micro-weighing system based on adaptive interferometer has potential for reducing the threshold of mass detection down to 10-17 g in the case of using a resonator with sub-micron dimensions
Frequency Adaptability of Harmonics Controllers for Grid-Interfaced Converters
DEFF Research Database (Denmark)
Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede
2016-01-01
sensitivity of the most popular harmonic controllers for grid-interfaced converters. The frequency adaptability of these harmonic controllers is evaluated in the presence of a variable grid frequency within a specified reasonable range, e.g., +-1% of the nominal grid frequency (50 Hz). Solutions...
Radio Frequency Interference Suppression for Landmine Detection by Quadrupole Resonance
Liu Guoqing; Jiang Yi; Xiong Hong; Li Jian; Barrall Geoffrey A
2006-01-01
The quadrupole resonance (QR) technology can be used as a confirming sensor for buried plastic landmine detection by detecting the explosives within the mine. We focus herein on the detection of TNT mines via the QR sensor. Since the frequency of the QR signal is located within the AM radio frequency band, the QR signal can be corrupted by strong radio frequency interferences (RFIs). Hence to detect the very weak QR signal, RFI mitigation is essential. Reference antennas, which receive RFIs ...
Analysis of Continuous Microseismic Recordings: Resonance Frequencies and Unconventional Events
Tary, J.; van der Baan, M.
2012-12-01
Hydrofracture experiments, where fluids and proppant are injected into reservoirs to create fractures and enhance oil recovery, are often monitored using microseismic recordings. The total stimulated volume is then estimated by the size of the cloud of induced micro-earthquakes. This implies that only brittle failure should occur inside reservoirs during the fracturing. Yet, this assumption may not be correct, as the total energy injected into the system is orders of magnitude larger than the total energy associated with brittle failure. Instead of using only triggered events, it has been shown recently that the frequency content of continuous recordings may also provide information on the deformations occurring inside reservoirs. Here, we use different kinds of time-frequency transforms to track the presence of resonance frequencies. We analyze different data sets using regular, long-period and broadband geophones. The resonance frequencies observed are mainly included in the frequency band of 5-60 Hz. We systematically examine first the possible causes of resonance frequencies, dividing them into source, path and receiver effects. We then conclude that some of the observed frequency bands likely result from source effects. The resonance frequencies could be produced by either interconnected fluid-filled fractures in the order of tens of meters, or by small repetitive events occurring at a characteristic periodicity. Still, other mechanisms may occur or be predominant during reservoir fracturing, depending on the lithology as well as the pressure and temperature conditions at depth. During one experiment, both regular micro-earthquakes, long-period long-duration events (LPLD) and resonance frequencies are observed. The lower part of the frequency band of these resonance frequencies (5-30 Hz) overlaps with the anticipated frequencies of observed LPLDs in other experiments (Hz). The exact origin of both resonance frequencies and LPLDs is still under debate
Multiplexed infrared photodetection using resonant radio-frequency circuits
Energy Technology Data Exchange (ETDEWEB)
Liu, R.; Lu, R.; Gong, S.; Wasserman, D. [Department of Electrical and Computer Engineering, University of Illinois Urbana Champaign, Urbana, Illinois 61801 (United States); Roberts, C. [Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts 01854 (United States); Allen, J. W.; Allen, M. S. [Air Force Research Laboratory, Munitions Directorate, Eglin Air Force Base, Florida 32542 (United States); Wenner, B. R. [Air Force Research Laboratory, Sensors Directorate, Wright Patterson Air Force Base, Ohio 45433 (United States)
2016-02-08
We demonstrate a room-temperature semiconductor-based photodetector where readout is achieved using a resonant radio-frequency (RF) circuit consisting of a microstrip split-ring resonator coupled to a microstrip busline, fabricated on a semiconductor substrate. The RF resonant circuits are characterized at RF frequencies as function of resonator geometry, as well as for their response to incident IR radiation. The detectors are modeled analytically and using commercial simulation software, with good agreement to our experimental results. Though the detector sensitivity is weak, the detector architecture offers the potential for multiplexing arrays of detectors on a single read-out line, in addition to high speed response for either direct coupling of optical signals to RF circuitry, or alternatively, carrier dynamics characterization of semiconductor, or other, material systems.
Acoustic Resonance Frequency Elimination Device for Safety Relief Valves
Energy Technology Data Exchange (ETDEWEB)
Redmond, J.
2014-07-01
Industry experience has shown that Safety Relief Valves (SRVs) and Steam Dryers installed in Boiling Water Reactors (BWRs) experience vibration induced degradation and failures caused by acoustic resonance vibration of the main steam lines, resulting in decreased reliability and potential safety issues. The resonance is caused by vortex shedding from the standpipe inlet and acoustic standing waves in the standpipe, occurring when the two frequencies match. (Author)
Investigation of Vertical Spiral Resonators for Low Frequency Metamaterial Design
Zhu, Jiwen; Stevens, Christopher J; Edwards, David J
2008-01-01
This paper thoroughly explores the characteristics of vertical spiral resonators (VSR). They exhibit rela-tively high Q factors and sizes around a few percent of the free space wavelength, which make them ideal candi-dates for assembling metamaterial devices. A quasistatic model of VSR is obtained from simple analytical ex-pressions, and the effects of certain geometrical parameters on the resonant frequency are investigated.
Installation and Commissioning of the Resonant Frequency Control Cooling System
Energy Technology Data Exchange (ETDEWEB)
Kwon, Hyeokjung; Seol, Kyungtae; Kim, Hansung; Jang, Jiho; Cho, Yongsub [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2013-05-15
Total 11 sets of Resonant Frequency Control Cooling System (RCCS) are used to control the resonance frequency of the 100-MeV DTL. The specifications of the RCCS are summarized. The RCCS should cover the temperature from 21 .deg. C to 33 .deg. C, heat load from magnet power only to full RF power in addition to the magnet power. The stability of the temperature control is less than 0.1 .deg. C. The control input variable comes from the resonance frequency error from the low level RF (LLRF) system. All RCCSs were installed and tested. In this paper, the installation and initial test results of the RCCS are presented. The standalone test of the RCCS for 100-MeV DTL was carried out. The results showed that the chiller temperature fluctuated above the specification mainly because the chiller controller was not properly tuned, but the RCCS with two independent control valves could be operated to give the required stability.
Relationship between wingbeat frequency and resonant frequency of the wing in insects
International Nuclear Information System (INIS)
In this study, we experimentally studied the relationship between wingbeat frequency and resonant frequency of 30 individuals of eight insect species from five orders: Odonata (Sympetrum flaveolum), Lepidoptera (Pieris rapae, Plusia gamma and Ochlodes), Hymenoptera (Xylocopa pubescens and Bombus rupestric), Hemiptera (Tibicen linnei) and Coleoptera (Allomyrina dichotoma). The wingbeat frequency of free-flying insects was measured using a high-speed camera while the natural frequency was determined using a laser displacement sensor along with a Bruel and Kjaer fast Fourier transform analyzer based on the base excitation method. The results showed that the wingbeat frequency was related to body mass (m) and forewing area (Af), following the proportionality f ∼ m1/2/Af, while the natural frequency was significantly correlated with area density (f0 ∼ mw/Af, mw is the wing mass). In addition, from the comparison of wingbeat frequency to natural frequency, the ratio between wingbeat frequency and natural frequency was found to be, in general, between 0.13 and 0.67 for the insects flapping at a lower wingbeat frequency (less than 100 Hz) and higher than 1.22 for the insects flapping at a higher wingbeat frequency (higher than 100 Hz). These results suggest that wingbeat frequency does not have a strong relation with resonance frequency: in other words, insects have not been evolved sufficiently to flap at their wings' structural resonant frequency. This contradicts the general conclusion of other reports-–that insects flap at their wings' resonant frequency to take advantage of passive deformation to save energy. (paper)
Microwave-frequency electromechanical resonators incorporating phononic crystals
Satzinger, K. J.; Peairs, G.; Vainsencher, A.; Cleland, A. N.
Piezoelectric micromechanical resonators at gigahertz frequencies have been operated in the quantum limit, with quantum control and measurement achieved using superconducting qubits. However, experiments to date have been limited by mechanical dissipation, due to a combination of internal and radiative losses. In this talk, we explore the incorporation of phononic crystals into resonator designs. In phononic crystals, periodic patterning manipulates the acoustic band structure of the material. Through appropriately chosen geometries, these periodic patterns lead to full acoustic bandgaps which can be used to greatly reduce radiation losses from resonant structures. Alternatively, the crystal geometry can be manipulated to allow isolated modes within the bandgap, giving fine control over the spatial structure of the resonator modes. In this talk, we will describe the design, fabrication, and measurement of resonators with phononic crystals.
Adaptive Radio Frequency Interference Mitigation for HF Surface Wave Radar
Institute of Scientific and Technical Information of China (English)
WAN Xian-rong; KE Heng-yu; CHENG Feng
2005-01-01
The paper analyses the characteristics of radio frequency interference (RFI) in HF surface wave radar (HFSWR) which adopts the linear frequency modulated interrupted continuous wave (FMICW). RFI will influence all the range cells including all the positive frequency and negative frequency, and the negative frequency range cells contain only the interference information. Based on the above characteristics, we introduce and analyze a new adaptive interference mitigation beamforming algorithm using the negative frequency range cells samples to estimate the interference covariance matrix. Experimental results confirm that this general and robust algorithm can achieve effective RFI suppression using the data recorded by the HFSWR, located near Zhoushan in Zhejiang China.
Frequency-scanning marginal oscillator for ion cyclotron resonance spectroscopy
Kemper, Paul R.; Bowers, Michael T.
1982-07-01
A number of ion cyclotron resonance applications have arisen in the past few years which require a frequency-scanned detection system. Since the traditional marginal oscillator detector has always been a fixed-frequency detector, alternative detection techniques such as bridge circuit detectors have become widely used. In this paper we present an alternative to the bridge detector, namely, a frequency-scanning marginal oscillator. Requirements and modifications necessary to convert a marginal oscillator to frequency scanning operation are discussed in detail and the necessary circuit diagrams presented. Finally, a theoretical comparison is made between bridge circuit and marginal oscillator sensitivities.
Artificial excitation of ELF waves with frequency of Schumann resonance
Streltsov, A. V.; Guido, T.; Tulegenov, B.; Labenski, J.; Chang, C.-L.
2014-11-01
We report results from the experiment aimed at the artificial excitation of extremely low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance. Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the Earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range 7.8-8.0 Hz when the ionosphere has a strong F layer, the frequency of the HF radiation is in the range 3.20-4.57 MHz, and the electric field greater than 5 mV/m is present in the ionosphere.
Frequency-swept detector for ion cyclotron resonance mass spectrometers
Wronka, J.; Ridge, D. P.
1982-04-01
Design, construction, performance, and use of a frequency-swept bridge detector for ion cyclotron resonance mass spectrometry are described. Special features include characterization and simple automatic correction of phase shift to allow broadband detection. The result is a detection system that may be used either at constant field or constant frequency. Drift-mode operation is simplified in that it may be satisfactorily used without the various signal modulation schemes used in previous detectors. In the trapped mode the detector may be pulsed to control the timing of ion detection. This detector makes it possible to do frequency-swept double resonance experiments which provide spectra of all the product ions of a given reactant ion. Circuit schematics and typical frequency- and field-swept spectra are shown.
Frequency-tunable superconducting resonators via nonlinear kinetic inductance
Energy Technology Data Exchange (ETDEWEB)
Vissers, M. R.; Hubmayr, J.; Sandberg, M.; Gao, J. [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Chaudhuri, S. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Bockstiegel, C. [Department of Physics, University of California, Santa Barbara, California 93106 (United States)
2015-08-10
We have designed, fabricated, and tested a frequency-tunable high-Q superconducting resonator made from a niobium titanium nitride film. The frequency tunability is achieved by injecting a DC through a current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent. We have demonstrated continuous tuning of the resonance frequency in a 180 MHz frequency range around 4.5 GHz while maintaining the high internal quality factor Q{sub i} > 180 000. This device may serve as a tunable filter and find applications in superconducting quantum computing and measurement. It also provides a useful tool to study the nonlinear response of a superconductor. In addition, it may be developed into techniques for measurement of the complex impedance of a superconductor at its transition temperature and for readout of transition-edge sensors.
Numerical modeling of seismic waves using frequency-adaptive meshes
Hu, Jinyin; Jia, Xiaofeng
2016-08-01
An improved modeling algorithm using frequency-adaptive meshes is applied to meet the computational requirements of all seismic frequency components. It automatically adopts coarse meshes for low-frequency computations and fine meshes for high-frequency computations. The grid intervals are adaptively calculated based on a smooth inversely proportional function of grid size with respect to the frequency. In regular grid-based methods, the uniform mesh or non-uniform mesh is used for frequency-domain wave propagators and it is fixed for all frequencies. A too coarse mesh results in inaccurate high-frequency wavefields and unacceptable numerical dispersion; on the other hand, an overly fine mesh may cause storage and computational overburdens as well as invalid propagation angles of low-frequency wavefields. Experiments on the Padé generalized screen propagator indicate that the Adaptive mesh effectively solves these drawbacks of regular fixed-mesh methods, thus accurately computing the wavefield and its propagation angle in a wide frequency band. Several synthetic examples also demonstrate its feasibility for seismic modeling and migration.
Photonic measurement of microwave frequency using a silicon microdisk resonator
Liu, Li; Jiang, Fan; Yan, Siqi; Min, Shucun; He, Mengying; Gao, Dingshan; Dong, Jianji
2015-01-01
A simple photonic approach to the measurement of microwave signal frequency with adjustable measurement range and resolution is proposed and demonstrated. In this approach, the unknown microwave signal is converted to an optical signal with single sideband modulation. Subsequently, a notch microwave photonic filter (MPF) is implemented by employing a high-Q silicon microdisk resonator (MDR). The MPF is tunable by changing the frequency interval between the optical carrier and the MDR notch so as to obtain different amplitude responses. A fixed frequency-to-power mapping is established by obtaining an amplitude comparison function (ACF) of the microwave power ratio and the microwave frequency. A proof-of-concept experiment demonstrates a frequency measurement range of 10 GHz, with measurement error of ±0.1 GHz. Different frequency measurement ranges and resolutions are also discussed.
Adaptive Fourier Decomposition Based Time-Frequency Analysis
Institute of Scientific and Technical Information of China (English)
Li-Ming Zhang
2014-01-01
The attempt to represent a signal simultaneously in time and frequency domains is full of challenges. The recently proposed adaptive Fourier decomposition (AFD) offers a practical approach to solve this problem. This paper presents the principles of the AFD based time-frequency analysis in three aspects: instantaneous frequency analysis, frequency spectrum analysis, and the spectrogram analysis. An experiment is conducted and compared with the Fourier transform in convergence rate and short-time Fourier transform in time-frequency distribution. The proposed approach performs better than both the Fourier transform and short-time Fourier transform.
Adaptive Peak Frequency Estimation Using a Database of PARCOR Coefficients
Directory of Open Access Journals (Sweden)
Iiguni Youji
2005-01-01
Full Text Available This paper presents an adaptive peak frequency estimation method using a database that stores PARCOR coefficients as key attributes and the corresponding peak frequencies as nonkey attributes. The least-square lattice algorithm is used to recursively estimate the PARCOR coefficients to adapt to changing circumstances. The nearest neighbor to the current PARCOR coefficient is retrieved from the database, and the corresponding peak frequency is regarded as the estimation. A simultaneous execution of database construction and peak estimation with database update is performed to accelerate the processing time and to improve the estimation accuracy.
Effect of metal coating and residual stress on the resonant frequency of MEMS resonators
Indian Academy of Sciences (India)
Ashok Kumar Pandey; K P Venkatesh; Rudra Pratap
2009-08-01
MEMS resonators are designed for a ﬁxed resonant frequency. Therefore, any shift in the resonant frequency of the ﬁnal fabricated structure can be a denting factor for its suitability towards a desired application. There are numerous factors which alter the designed resonant frequency of the fabricated resonator such as the metal layer deposited on top of the beam and the residual stresses present in the fabricated structure. While the metal coating, which acts as electrode, increases the stiffness and the effective mass of the composite structure, the residual stress increases or decreases the net stiffness if it is a tensile or compressive type respectively. In this paper, we investigate both these cases by taking two different structures, namely, the micro cantilever beam with gold layer deposited on its top surface and the MEMS gyroscope with residual stresses. First, we carry out experiments to characterize both these structures to ﬁnd their resonant frequencies. Later, we analytically model those effects and compare them with the experimentally obtained values. Finally, it is found that the analytical models give an error of less than 10% with respect to the experimental results in both the cases.
Resonance frequency shift of strongly heated micro-cantilevers
Sandoval, Felipe Aguilar; Bertin, Éric; Bellon, Ludovic
2015-01-01
In optical detection setups to measure the deflection of micro-cantilevers, part of the sensing light is absorbed, heating the mechanical probe. We present experimental evidences of a frequency shift of the resonant modes of a cantilever when the light power of the optical measurement set-up is increased. This frequency shift is a signature of the temperature rise, and presents a dependence on the mode number. An analytical model is derived to take into account the temperature profile along the cantilever, it shows that the frequency shifts are given by an average of the profile weighted by the local curvature for each resonant mode. We apply this framework to measurements in vacuum and demonstrate that huge temperatures can be reached with moderate light intensities: a thousand {\\textdegree}C with little more than 10 mW. We finally present some insight into the physical phenomena when the cantilever is in air instead of vacuum.
Dynamics of multi-frequency oscillator ensembles with resonant coupling
Energy Technology Data Exchange (ETDEWEB)
Lueck, S. [Department of Physics and Astronomy, Potsdam University, Karl-Liebknecht-Str. 24-25, 14476 Potsdam (Germany); Pikovsky, A., E-mail: pikovsky@stat.physik.uni-potsdam.de [Department of Physics and Astronomy, Potsdam University, Karl-Liebknecht-Str. 24-25, 14476 Potsdam (Germany)
2011-07-11
We study dynamics of populations of resonantly coupled oscillators having different frequencies. Starting from the coupled van der Pol equations we derive the Kuramoto-type phase model for the situation, where the natural frequencies of two interacting subpopulations are in relation 2:1. Depending on the parameter of coupling, ensembles can demonstrate fully synchronous clusters, partial synchrony (only one subpopulation synchronizes), or asynchrony in both subpopulations. Theoretical description of the dynamics based on the Watanabe-Strogatz approach is developed. -- Highlights: → Kuramoto model is generalized on the case of resonantly interacting oscillators having frequency ratio 2:1. → Regimes of full and partial synchrony, as well as non-synchronous ones are reported. → Analytical description is developed on the basis of the Watanabe-Strogatz approach.
Detection of electron paramagnetic resonance absorption using frequency modulation
Hirata, Hiroshi; Kuyama, Toshifumi; Ono, Mitsuhiro; Shimoyama, Yuhei
2003-10-01
A frequency modulation (FM) method was developed to measure electron paramagnetic resonance (EPR) absorption. The first-derivative spectrum of 1,1-diphenyl-2-picrylhydrazyl (DPPH) powder was measured with this FM method. Frequency modulation of up to 1.6 MHz (peak-to-peak) was achieved at a microwave carrier frequency of 1.1 GHz. This corresponds to a magnetic field modulation of 57 μT (peak-to-peak) at 40.3 mT. By using a tunable microwave resonator and automatic control systems, we achieved a practical continuous-wave (CW) EPR spectrometer that incorporates the FM method. In the present experiments, the EPR signal intensity was proportional to the magnitude of frequency modulation. The background signal at the modulation frequency (1 kHz) for EPR detection was also proportional to the magnitude of frequency modulation. An automatic matching control (AMC) system reduced the amplitude of noise in microwave detection and improved the baseline stability. Distortion of the spectral lineshape was seen when the spectrometer settings were not appropriate, e.g., with a lack of the open-loop gain in automatic tuning control (ATC). FM is an alternative to field modulation when the side-effect of field modulation is detrimental for EPR detection. The present spectroscopic technique based on the FM scheme is useful for measuring the first derivative with respect to the microwave frequency in investigations of electron-spin-related phenomena.
A software sampling frequency adaptive algorithm for reducing spectral leakage
Institute of Scientific and Technical Information of China (English)
PAN Li-dong; WANG Fei
2006-01-01
Spectral leakage caused by synchronous error in a nonsynchronous sampling system is an important cause that reduces the accuracy of spectral analysis and harmonic measurement.This paper presents a software sampling frequency adaptive algorithm that can obtain the actual signal frequency more accurately,and then adjusts sampling interval base on the frequency calculated by software algorithm and modifies sampling frequency adaptively.It can reduce synchronous error and impact of spectral leakage;thereby improving the accuracy of spectral analysis and harmonic measurement for power system signal where frequency changes slowly.This algorithm has high precision just like the simulations show,and it can be a practical method in power system harmonic analysis since it can be implemented easily.
Analytical investigation into the resonance frequencies of a curling probe
Arshadi, Ali; Brinkmann, Ralf Peter
2016-08-01
The term ‘active plasma resonance spectroscopy’ (APRS) denotes a class of closely related plasma diagnostic methods which utilize the natural ability of plasmas to resonate on or near the electron plasma frequency {ω\\text{pe}} ; an electrical radio frequency signal (in the GHz range) is coupled into the plasma via an antenna or a probe, the spectral response is recorded and a mathematical model is employed to determine plasma parameters such as the plasma density and the electron temperature. The curling probe, recently invented by Liang et al (2011 Appl. Phys. Express 4 066101), is a novel realization of the APRS concept which has many practical advantages. In particular, it can be miniaturized and flatly embedded into the chamber wall, thus allowing the monitoring of plasma processes without contamination nor disturbance. Physically, the curling probe can be understood as a ‘coiled’ form of the hairpin probe (Stenzel 1976 Rev. Sci. Instrum. 47 603). Assuming that the spiralization of the probe has little electrical effect, this paper investigates the characteristcs of a ‘straightened’ curling probe by modeling it as an infinite slot-type resonator that is in direct contact with the plasma. The diffraction of an incident plane wave at the slot is calculated by solving the cold plasma model and Maxwell’s equations simultaneously. The resonance frequencies of the probe are derived and are found to be in good agreement with the numerical results of the probe inventors.
Black phosphorus nanoelectromechanical resonators vibrating at very high frequencies
Wang, Zenghui; Jia, Hao; Zheng, Xuqian; Yang, Rui; Wang, Zefang; Ye, G. J.; Chen, X. H.; Shan, Jie; Feng, Philip X.-L.
2014-12-01
We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ~100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ~200 nm down to ~20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory devices and for semiconductor transducers where high-speed mechanical motions could be coupled to the attractive electronic and optoelectronic properties of black phosphorus.We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ~100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ~200 nm down to ~20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory
Note: On-line weak signal detection via adaptive stochastic resonance.
Lu, Siliang; He, Qingbo; Kong, Fanrang
2014-06-01
We design an instrument with a novel embedded adaptive stochastic resonance (SR) algorithm that consists of a SR module and a digital zero crossing detection module for on-line weak signal detection in digital signal processing applications. The two modules are responsible for noise filtering and adaptive parameter configuration, respectively. The on-line weak signal detection can be stably achieved in seconds. The prototype instrument exhibits an advance of 20 dB averaged signal-to-noise ratio and 5 times averaged adjust R-square as compared to the input noisy signal, in considering different driving frequencies and noise levels.
Increasing ferromagnetic resonance frequency using lamination and shape
El-Ghazaly, A.; White, R. M.; Wang, S. X.
2015-05-01
The magnetic permeability frequency spectrum is one of the most critical properties for the operation of high frequency magnetic devices in the gigahertz regime. Permeability is fairly constant up to the ferromagnetic resonance (FMR) frequency, at which point the relative permeability drops to unity. Extending FMR to higher frequencies is thus imperative for developing GHz-range magnetic devices. The simulation and experimental investigations presented in this paper demonstrate how stacking layers to form a laminated film increases the FMR frequency by allowing flux closure between layers along the induced easy-axis direction. This flux closure reduces the demagnetization factor along the easy-axis direction by two orders of magnitude. This effect, however, is only observable in patterned films where the shape anisotropy is enough to result in variation of the FMR frequency. Experiments using patterned magnetic cores were performed to illustrate this effect. Through detailed investigation of the permeability spectra of both single layer and laminated CoTaZr magnetic films patterned into 500 μm × L films (where L ranged from 200 μm to 1000 μm), the FMR frequency was extracted and proven to increase as a result of lamination. The degree to which the frequency is boosted by lamination increases exponentially as the length of the film is decreased. Through a combination of lamination and shape demagnetization, the effective anisotropy, which directly relates to FMR frequency, was shown to increase by about 100%.
On geometrical scaling of split-ring and double-bar resonators at optical frequencies
Tretyakov, Sergei
2006-01-01
In this paper we consider the resonant frequency of split-ring resonators and double-bar resonators used to create artificial magnetic response at terahertz and optical frequencies. It is known that geometrical scaling of the resonant frequency of split rings breaks down at high frequencies (in the visible) due to electromagnetic properties of metals at those frequencies. Here we will discuss this phenomenon in terms of equivalent inductance and capacitance of the ring, derive an approximate ...
Fast Adaptive Beamforming with Smart Antenna for Radio Frequency Repeater
Directory of Open Access Journals (Sweden)
Wang Chaoqun
2016-01-01
Full Text Available We present a fast adaptive beamforming null algorithm with smart antenna for Radio Frequency Repeater (RFR. The smart antenna system is realized by a Direction Of Arrival (DOA Estimator, whose output is used by an adaptive beamforming algorithm to shape a suitable radiation pattern of the equivalent antenna; so that the co-channel interference due to retransmitting antenna can be reduced. The proposed adaptive beamforming algorithm, which has been proved by formulaic analysis and simulation, has a lower computation complexity yet better performance.
Tunable frequency combs based on dual microring resonators
Miller, Steven A; Ramelow, Sven; Luke, Kevin; Dutt, Avik; Farsi, Alessandro; Gaeta, Alexander L; Lipson, Michal
2015-01-01
In order to achieve efficient parametric frequency comb generation in microresonators, external control of coupling between the cavity and the bus waveguide is necessary. However, for passive monolithically integrated structures, the coupling gap is fixed and cannot be externally controlled, making tuning the coupling inherently challenging. We design a dual-cavity coupled microresonator structure in which tuning one ring resonance frequency induces a change in the overall cavity coupling condition. We demonstrate wide extinction tunability with high efficiency by engineering the ring coupling conditions. Additionally, we note a distinct dispersion tunability resulting from coupling two cavities of slightly different path lengths, and present a new method of modal dispersion engineering. Our fabricated devices consist of two coupled high quality factor silicon nitride microresonators, where the extinction ratio of the resonances can be controlled using integrated microheaters. Using this extinction tunability...
Eveno, Pauline; Kieffer, Benoît; Gilbert, Joël; Petiot, Jean-François; Caussé, René
2012-01-01
International audience Measurements and calculations of the input impedance of wind musical instruments are now well mastered. The purpose of this work is to study experimentally how far the resonance frequencies of brass instruments, taken from their input impedance, are able to give informations about the playing frequencies. Three different trumpets, obtained by changing only the leadpipe of the same instrument, were considered for the experiment. After a measurement of the input impeda...
Computing resonant frequency of C-shaped compact microstrip antennas by using ANFIS
Akdagli, Ali; Kayabasi, Ahmet; Develi, Ibrahim
2015-03-01
In this work, the resonant frequency of C-shaped compact microstrip antennas (CCMAs) operating at UHF band is computed by using the adaptive neuro-fuzzy inference system (ANFIS). For this purpose, 144 CCMAs with various relative dielectric constants and different physical dimensions were simulated by the XFDTD software package based on the finite-difference time domain (FDTD) method. One hundred and twenty-nine CCMAs were employed for training, while the remaining 15 CCMAs were used for testing of the ANFIS model. Average percentage error (APE) values were obtained as 0.8413% and 1.259% for training and testing, respectively. In order to demonstrate its validity and accuracy, the proposed ANFIS model was also tested over the simulation data given in the literature, and APE was obtained as 0.916%. These results show that ANFIS can be successfully used to compute the resonant frequency of CCMAs.
Full investigation of the resonant frequency servo loop for resonator fiber-optic gyro.
Ma, Huilian; Lu, Xiao; Yao, Linzhi; Yu, Xuhui; Jin, Zhonghe
2012-07-20
Resonator fiber-optic gyro (RFOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A high-accuracy resonant frequency servo loop is indispensable for a high-performance RFOG. It is composed of a frequency discriminator, a loop filter, and a laser actuator. Influences of the loop parameters are fully developed. Optimized loop parameters are obtained by considering the noise reduction and wide dynamic performance of the RFOG. As a result, with the integration time of 10 s, the accuracy of the resonant frequency loop is increased to 0.02 Hz (1σ). It is equivalent to a rotation rate of 0.067°/h, which is close to the shot noise limit for the RFOG, while a minimum rotation of ±0.05°/s has been carried out simultaneously. These are the best results reported to date, to the best of our knowledge, for an RFOG using the miniature semiconductor laser that benefits from the optimization of the resonant frequency servo-loop parameters.
Frequency-selective analysis of multichannel magnetic resonance spectroscopy data.
Sandgren, Niclas; Stoica, Petre
2005-01-01
In several practical magnetic resonance spectroscopy (MRS) applications the user is interested only in the spectral content of a specific frequency band of the spectrum. A frequency-selective (or sub-band) method estimates only the parameters of those spectroscopic components that lie in a pre-selected frequency band of the spectrum in a computationally efficient manner. Multichannel MRS is a technique that employs phased-array receive coils to increase the signal-to-noise ratio (SNR) in the spectra by combining several simultaneous measurements of the magnetic resonance (MR) relaxation of an excited sample. In this paper we suggest a frequency-selective multichannel parameter estimation approach that combines the appealing features (high speed and improved SNR) of the two techniques above. The presented method shows parameter estimation accuracies comparable to those of existing fullband multichannel techniques in the high SNR case, but at a considerably lower computational complexity, and significantly better parameter estimation accuracies in low SNR scenarios. PMID:17282712
Nano-resonator frequency response based on strain gradient theory
International Nuclear Information System (INIS)
This paper aims to explore the dynamic behaviour of a nano-resonator under ac and dc excitation using strain gradient theory. To achieve this goal, the partial differential equation of nano-beam vibration is first converted to an ordinary differential equation by the Galerkin projection method and the lumped model is derived. Lumped parameters of the nano-resonator, such as linear and nonlinear springs and damper coefficients, are compared with those of classical theory and it is demonstrated that beams with smaller thickness display greater deviation from classical parameters. Stable and unstable equilibrium points based on classic and non-classical theories are also compared. The results show that, regarding the applied dc voltage, the dynamic behaviours expected by classical and non-classical theories are significantly different, such that one theory predicts the un-deformed shape as the stable condition, while the other theory predicts that the beam will experience bi-stability. To obtain the frequency response of the nano-resonator, a general equation including cubic and quadratic nonlinearities in addition to parametric electrostatic excitation terms is derived, and the analytical solution is determined using a second-order multiple scales method. Based on frequency response analysis, the softening and hardening effects given by two theories are investigated and compared, and it is observed that neglecting the size effect can lead to two completely different predictions in the dynamic behaviour of the resonators. The findings of this article can be helpful in the design and characterization of the size-dependent dynamic behaviour of resonators on small scales. (paper)
A study of trapped mode resonances in asymmetric X-shape resonator for frequency selective surface
Chen, Kejian; Liu, Hong; Wang, Yiqi; Zhu, Yiming
2013-08-01
FSS is a two-dimensional periodic array of resonating metallic-dielectric structures, When FSS device steps into Terahertz range from microwave range, it is studied as THz functional components (such as Terahertz filter, Terahertz biochemical sensor, etc.) to promote the functionality of the THz spectroscopy/imaging system. When the device requires a narrow band transmission window for frequency selecting or a high electric field concentration in certain area to improve its sensitivity for sensing, normally, a high quality (Q) resonant structure can give helps. Recently, high-Q resonance induced by trapped mode resonance i studied widely in FSS research areas. To induce trapped mode resonance, one can simply break the symmetric of the unit structure of FSS. In this paper, several asymmetric X-shaped resonators for FSS working in terahertz range have been studied numerically. To compare the behaviour of X-shape resonator under different conditions (with additional part: Heart lines, Shoulder lines, Wrap or Shoes squares), a common platform (θ=60, θis angle of X shape) which is suitable for most of cases was used to make the study more meaningful. As the field enhancement behaviour is related to the trapped mode introduced by the asymmetric structure, we propose such kind of device to be used as a high quality filter or as a sensing element for biochemical samples.
About resonance frequencies of aluminium alloy bending vibrations
International Nuclear Information System (INIS)
Using ultrasonic method resonance frequencies of bending vibrations and elastic moduli of aluminium alloy SAV-1 samples are investigated. On the base of spectra of bending vibrations in low-frequency range data on values of a number of elastic properties are obtained as well as dispersion characteristics of main moduli for number of frequencies before and after ionizing irradiation (60Co, 5x103-1.6x107 Gy) of samples. Considerable stability of sample elastic moduli during common storage conditions and nonlinear dose dependence of these parameters within wide range of absorbed doses are pointed out. Possible causes of revealed effects of radiation modification of elastic properties of SAV-1 alloy are analyzed
Radio Frequency Interference Suppression for Landmine Detection by Quadrupole Resonance
Directory of Open Access Journals (Sweden)
Liu Guoqing
2006-01-01
Full Text Available The quadrupole resonance (QR technology can be used as a confirming sensor for buried plastic landmine detection by detecting the explosives within the mine. We focus herein on the detection of TNT mines via the QR sensor. Since the frequency of the QR signal is located within the AM radio frequency band, the QR signal can be corrupted by strong radio frequency interferences (RFIs. Hence to detect the very weak QR signal, RFI mitigation is essential. Reference antennas, which receive RFIs only, can be used together with the main antenna, which receives both the QR signal and the RFIs, for RFI mitigation. The RFIs are usually colored both spatially and temporally, and hence exploiting only the spatial diversity of the antenna array may not give the best performance. We exploit herein both the spatial and temporal correlations of the RFIs to improve the TNT detection performance.
Yu, Haitao; Guo, Xinmeng; Wang, Jiang; Deng, Bin; Wei, Xile
2015-10-01
The phenomenon of vibrational resonance is investigated in adaptive Newman-Watts small-world neuronal networks, where the strength of synaptic connections between neurons is modulated based on spike-timing-dependent plasticity. Numerical results demonstrate that there exists appropriate amplitude of high-frequency driving which is able to optimize the neural ensemble response to the weak low-frequency periodic signal. The effect of networked vibrational resonance can be significantly affected by spike-timing-dependent plasticity. It is shown that spike-timing-dependent plasticity with dominant depression can always improve the efficiency of vibrational resonance, and a small adjusting rate can promote the transmission of weak external signal in small-world neuronal networks. In addition, the network topology plays an important role in the vibrational resonance in spike-timing-dependent plasticity-induced neural systems, where the system response to the subthreshold signal is maximized by an optimal network structure. Furthermore, it is demonstrated that the introduction of inhibitory synapses can considerably weaken the phenomenon of vibrational resonance in the hybrid small-world neuronal networks with spike-timing-dependent plasticity.
Sparse time-frequency decomposition based on dictionary adaptation.
Hou, Thomas Y; Shi, Zuoqiang
2016-04-13
In this paper, we propose a time-frequency analysis method to obtain instantaneous frequencies and the corresponding decomposition by solving an optimization problem. In this optimization problem, the basis that is used to decompose the signal is not known a priori. Instead, it is adapted to the signal and is determined as part of the optimization problem. In this sense, this optimization problem can be seen as a dictionary adaptation problem, in which the dictionary is adaptive to one signal rather than a training set in dictionary learning. This dictionary adaptation problem is solved by using the augmented Lagrangian multiplier (ALM) method iteratively. We further accelerate the ALM method in each iteration by using the fast wavelet transform. We apply our method to decompose several signals, including signals with poor scale separation, signals with outliers and polluted by noise and a real signal. The results show that this method can give accurate recovery of both the instantaneous frequencies and the intrinsic mode functions.
Effect of Geometry in Frequency Response Modeling of Nanomechanical Resonators
DEFF Research Database (Denmark)
Esfahania, M. Nasr; Yilmaz, M.; Sonne, Mads Rostgaard;
2016-01-01
The trend towards nanomechanical resonator sensors with increasing sensitivity raises the need to address challengesencountered in the modeling of their mechanical behavior. Selecting the best approach in mechanical response modelingamongst the various potential computational solid mechanics...... methods is subject to controversy. A guideline for theselection of the appropriate approach for a specific set of geometry and mechanical properties is needed. In this study, geometricallimitations in frequency response modeling of flexural nanomechanical resonators are investigated. Deviation of......Euler and Timoshenko beam theories from numerical techniques including finite element modeling and Surface Cauchy-Borntechnique are studied. The results provide a limit beyond which surface energy contribution dominates the mechanical behavior.Using the Surface Cauchy-Born technique as the reference, a maximum error...
Cosci, Alessandro; Berneschi, Simone; Giannetti, Ambra; Farnesi, Daniele; Cosi, Franco; Baldini, Francesco; Nunzi Conti, Gualtiero; Soria, Silvia; Barucci, Andrea; Righini, Giancarlo; Pelli, Stefano
2016-01-01
This work shows the improvements in the sensing capabilities and precision of an Optical Microbubble Resonator due to the introduction of an encaging poly(methyl methacrylate) (PMMA) box. A frequency fluctuation parameter σ was defined as a score of resonance stability and was evaluated in the presence and absence of the encaging system and in the case of air- or water-filling of the cavity. Furthermore, the noise interference introduced by the peristaltic and the syringe pumping system was studied. The measurements showed a reduction of σ in the presence of the encaging PMMA box and when the syringe pump was used as flowing system. PMID:27589761
Frequency Response Adaptive Control of a Refrigeration Cycle
Directory of Open Access Journals (Sweden)
Jens G. Balchen
1989-01-01
Full Text Available A technique for the adaptation of controller parameters in a single control loop based upon the estimation of frequency response parameters has been presented in an earlier paper. This paper contains an extension and a generalization of the first method and results in a more versatile solution which is applicable to a wider range of process characteristics. The application of this adaptive control technique is illustrated by a laboratory refrigeration cycle in which the evaporator pressure controls the speed of the compressor.
International Nuclear Information System (INIS)
We present a novel method to determine the resonant frequency and quality factor of microwave resonators which is faster, more stable, and conceptually simpler than the yet existing techniques. The microwave resonator is pumped with the microwave radiation at a frequency away from its resonance. It then emits an exponentially decaying radiation at its eigen-frequency when the excitation is rapidly switched off. The emitted microwave signal is down-converted with a microwave mixer, digitized, and its Fourier transformation (FT) directly yields the resonance curve in a single shot. Being a FT based method, this technique possesses the Fellgett (multiplex) and Connes (accuracy) advantages and it conceptually mimics that of pulsed nuclear magnetic resonance. We also establish a novel benchmark to compare accuracy of the different approaches of microwave resonator measurements. This shows that the present method has similar accuracy to the existing ones, which are based on sweeping or modulating the frequency of the microwave radiation
Energy Technology Data Exchange (ETDEWEB)
Gyüre, B.; Márkus, B. G.; Bernáth, B.; Simon, F., E-mail: ferenc.simon@univie.ac.at [Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Spintronics Research Group (PROSPIN), P.O. Box 91, H-1521 Budapest (Hungary); Murányi, F. [Foundation for Research on Information Technologies in Society (IT’IS), Zeughausstrasse 43, 8004 Zurich (Switzerland)
2015-09-15
We present a novel method to determine the resonant frequency and quality factor of microwave resonators which is faster, more stable, and conceptually simpler than the yet existing techniques. The microwave resonator is pumped with the microwave radiation at a frequency away from its resonance. It then emits an exponentially decaying radiation at its eigen-frequency when the excitation is rapidly switched off. The emitted microwave signal is down-converted with a microwave mixer, digitized, and its Fourier transformation (FT) directly yields the resonance curve in a single shot. Being a FT based method, this technique possesses the Fellgett (multiplex) and Connes (accuracy) advantages and it conceptually mimics that of pulsed nuclear magnetic resonance. We also establish a novel benchmark to compare accuracy of the different approaches of microwave resonator measurements. This shows that the present method has similar accuracy to the existing ones, which are based on sweeping or modulating the frequency of the microwave radiation.
Superconducting radio-frequency resonator in magnetic fields up to 6 T
Ebrahimi, M. S.; Stallkamp, N.; Quint, W.; Wiesel, M.; Vogel, M.; Martin, A.; Birkl, G.
2016-07-01
We have measured the characteristics of a superconducting radio-frequency resonator in an external magnetic field. The magnetic field strength has been varied with 10 mT resolution between zero and 6 T. The resonance frequency and the quality factor of the resonator have been found to change significantly as a function of the magnetic field strength. Both parameters show a hysteresis effect which is more pronounced for the resonance frequency. Quantitative knowledge of such behaviour is particularly important when experiments require specific values of resonance frequency and quality factor or when the magnetic field is changed while the resonator is in the superconducting state.
Optical sum-frequency generation in whispering gallery mode resonators
Strekalov, Dmitry V; Huang, Yu-Ping; Kumar, Prem
2013-01-01
We demonstrate sum-frequency generation in a nonlinear whispering gallery mode resonator between a telecom wavelength and the Rb D2 line, achieved through natural phase matching. Due to the strong optical field confinement and ultra high Q of the cavity, we achieve a 1000-fold enhancement in the conversion efficiency compared to existing waveguide-based devices. The experimental data are in agreement with the nonlinear dynamics and phase matching theory in the spherical geometry employed. The experimental and theoretical results point to a new platform to manipulate the color and quantum states of light waves toward applications such as atomic memory based quantum networking and logic operations with optical signals.
RF MEMS Fractal Capacitors With High Self-Resonant Frequencies
Elshurafa, Amro M.
2012-07-23
This letter demonstrates RF microelectromechanical systems (MEMS) fractal capacitors possessing the highest reported self-resonant frequencies (SRFs) in PolyMUMPS to date. Explicitly, measurement results show SRFs beyond 20 GHz. Furthermore, quality factors higher than 4 throughout a band of 1-15 GHz and reaching as high as 28 were achieved. Additional benefits that are readily attainable from implementing fractal capacitors in MEMS are discussed, including suppressing residual stress warping, eliminating the need for etching holes, and reducing parasitics. The latter benefits were acquired without any fabrication intervention. © 2011 IEEE.
Blade Crack Detection of Centrifugal Fan Using Adaptive Stochastic Resonance
Bingbing Hu; Bing Li
2015-01-01
Centrifugal fans are widely used in various industries as a kind of turbo machinery. Among the components of the centrifugal fan, the impeller is a key part because it is used to transform kinetic energy into pressure energy. Crack in impeller’s blades is one of the serious hidden dangers. It is important to detect the cracks in the blades as early as possible. Based on blade vibration signals, this research applies an adaptive stochastic resonance (ASR) method to diagnose crack fault in cent...
Adaptive frequency estimation by MUSIC (Multiple Signal Classification) method
Karhunen, Juha; Nieminen, Esko; Joutsensalo, Jyrki
During the last years, the eigenvector-based method called MUSIC has become very popular in estimating the frequencies of sinusoids in additive white noise. Adaptive realizations of the MUSIC method are studied using simulated data. Several of the adaptive realizations seem to give in practice equally good results as the nonadaptive standard realization. The only exceptions are instantaneous gradient type algorithms that need considerably more samples to achieve a comparable performance. A new method is proposed for constructing initial estimates to the signal subspace. The method improves often dramatically the performance of instantaneous gradient type algorithms. The new signal subspace estimate can also be used to define a frequency estimator directly or to simplify eigenvector computation.
Ion cyclotron resonance bridge detector for frequency sweep
Energy Technology Data Exchange (ETDEWEB)
Pitsakis, M.N.; Wobschall, D.C.
1983-11-01
An electronic ion cyclotron resonance detection system was designed and constructed. The ions are excited by sweeping the frequency of the electric field (3--300 kHz) using a sweep frequency generator with a nonlinear sweep voltage in order to maintain an approximately constant mass resolution. Ion detection is accomplished by a bridge with a phase-sensitive detector as a demodulator. The required reference signal for the phase-sensitive detector is generated by a circuit with a transfer function which approximates that of the ICR signal in order to obtain an accurate phase match between the signal source and the detector. The device is capable of detecting a minimum concentration of 50 ions/cm/sup 3/ over a mass range of 15 to 1500 amu.
Ion cyclotron resonance bridge detector for frequency sweep
Pitsakis, Michael N.; Wobschall, Darold C.
1983-11-01
An electronic ion cyclotron resonance detection system was designed and constructed. The ions are excited by sweeping the frequency of the electric field (3-300 kHz) using a sweep frequency generator with a nonlinear sweep voltage in order to maintain an approximately constant mass resolution. Ion detection is accomplished by a bridge with a phase-sensitive detector as a demodulator. The required reference signal for the phase-sensitive detector is generated by a circuit with a transfer function which approximates that of the ICR signal in order to obtain an accurate phase match between the signal source and the detector. The device is capable of detecting a minimum concentration of 50 ions/cm3 over a mass range of 15 to 1500 amu.
Frequency locking in hair cells: Distinguishing between distinct resonant mechanisms
Edri, Yuval; Yochelis, Arik
2016-01-01
The auditory system displays remarkable mechanical sensitivity and frequency discrimination. These attributes have been shown to rely on an amplification process, which requires biochemical feedback loops. In some systems, the active process was shown to lead to spontaneous oscillations of hair cell bundles. In the last decade, models that display proximity to an oscillatory onset (a.k.a. Hopf bifurcation) have gained increasing support due to many advantages in explaining the hearing phenomenology. Particularly, they exhibit resonant responses to distinct frequencies of incoming sound waves. Unlike previous studies, two types of driving forces are being examined: additive, in which the external forcing term does not couple directly on the systems observable (passive coupling), and parametric, in which the forcing term directly affects the observable and thus intrinsically modifies the systems properties (active coupling). By applying universal principles near the Hopf bifurcation onset, we find several funda...
Resonant-frequency discharge in a multi-cell radio frequency cavity
Energy Technology Data Exchange (ETDEWEB)
Popovic, S; Upadhyay, J; Mammosser, J; Nikolic, M; Vuskovic, L
2014-11-07
We are reporting experimental results on microwave discharge operating at resonant frequency in a multi-cell radio frequency (RF) accelerator cavity. Although the discharge operated at room temperature, the setup was constructed so that it could be used for plasma generation and processing in fully assembled active superconducting radio-frequency (SRF) cryomodule (in situ operation). This discharge offers an efficient mechanism for removal of a variety of contaminants, organic or oxide layers, and residual particulates from the interior surface of RF cavities through the interaction of plasma-generated radicals with the cavity walls. We describe resonant RF breakdown conditions and address the problems related to generation and sustaining the multi-cell cavity plasma, which are breakdown and resonant detuning. We have determined breakdown conditions in the cavity, which was acting as a plasma vessel with distorted cylindrical geometry. We discuss the spectroscopic data taken during plasma removal of contaminants and use them to evaluate plasma parameters, characterize the process, and estimate the volatile contaminant product removal.
Planetary gearbox fault diagnosis using an adaptive stochastic resonance method
Lei, Yaguo; Han, Dong; Lin, Jing; He, Zhengjia
2013-07-01
Planetary gearboxes are widely used in aerospace, automotive and heavy industry applications due to their large transmission ratio, strong load-bearing capacity and high transmission efficiency. The tough operation conditions of heavy duty and intensive impact load may cause gear tooth damage such as fatigue crack and teeth missed etc. The challenging issues in fault diagnosis of planetary gearboxes include selection of sensitive measurement locations, investigation of vibration transmission paths and weak feature extraction. One of them is how to effectively discover the weak characteristics from noisy signals of faulty components in planetary gearboxes. To address the issue in fault diagnosis of planetary gearboxes, an adaptive stochastic resonance (ASR) method is proposed in this paper. The ASR method utilizes the optimization ability of ant colony algorithms and adaptively realizes the optimal stochastic resonance system matching input signals. Using the ASR method, the noise may be weakened and weak characteristics highlighted, and therefore the faults can be diagnosed accurately. A planetary gearbox test rig is established and experiments with sun gear faults including a chipped tooth and a missing tooth are conducted. And the vibration signals are collected under the loaded condition and various motor speeds. The proposed method is used to process the collected signals and the results of feature extraction and fault diagnosis demonstrate its effectiveness.
Blade Crack Detection of Centrifugal Fan Using Adaptive Stochastic Resonance
Directory of Open Access Journals (Sweden)
Bingbing Hu
2015-01-01
Full Text Available Centrifugal fans are widely used in various industries as a kind of turbo machinery. Among the components of the centrifugal fan, the impeller is a key part because it is used to transform kinetic energy into pressure energy. Crack in impeller’s blades is one of the serious hidden dangers. It is important to detect the cracks in the blades as early as possible. Based on blade vibration signals, this research applies an adaptive stochastic resonance (ASR method to diagnose crack fault in centrifugal fan. The ASR method, which can utilize the optimization ability of the grid search method and adaptively realize the optimal stochastic resonance system matching input signals, may weaken the noise and highlight weak characteristic and thus can diagnose the fault accurately. A centrifugal fan test rig is established and experiments with three cases of blades are conducted. In comparison with the ensemble empirical mode decomposition (EEMD analysis and the traditional Fourier transform method, the experiment verified the effectiveness of the current method in blade crack detection.
Wideband bioimpedance meter with the adaptive selection of frequency grid
Directory of Open Access Journals (Sweden)
V. S. Mosiychuk
2014-06-01
Full Text Available Introduction. For the diagnosis of functional state and structure of biological objects with weakly expressed irregularities it is important quickly and accurately to determine the amplitude- and phase-frequency characteristics. Therefore, the purpose of the article is a representation of the results of the development of biological objects high-speed impedance meter with the ability to select adaptive grid measuring frequencies in the extended band. Structure of the impedance meter. Developed instrument is designed to measure the impedance of the object on four-electrode method. The device uses a frequency synthesizer amplitude-phase detector integrally fabricated and active electrodes, by which the voltage controlled current source and the input buffer amplifiers with low input capacitance, are located in close proximity to the studied bioobject. This allowed to make measurements at frequencies up to 5 MHz. Instruments characteristics. To test the device characteristics the frequency characteristics of the test object (RC-chain impedance were measured. It is composed of 5 precision resistors and capacitors. Parameters of the elements were measured preliminarily by laboratory inductance, capacitance and resistance meter E7-12. The dependence of the measurement errors of the developed device in the frequency range from 1 kHz to 5 MHz is not more than 5% of the modulus of the impedance and not more than 2° of the phase.
DEFF Research Database (Denmark)
Tang, Yi; Yao, Wenli; Loh, Poh Chiang;
2015-01-01
This paper proposes a novel LCL-filter design method and its current control for grid-connected converters. With the proposed design method, it is possible to set the resonance frequency of the LCL-filter to be higher than the Nyquist frequency, i.e. half of the system sampling frequency, and thi......This paper proposes a novel LCL-filter design method and its current control for grid-connected converters. With the proposed design method, it is possible to set the resonance frequency of the LCL-filter to be higher than the Nyquist frequency, i.e. half of the system sampling frequency...
Frequency adaptation for enhanced radiation force amplitude in dynamic elastography.
Ouared, Abderrahmane; Montagnon, Emmanuel; Kazemirad, Siavash; Gaboury, Louis; Robidoux, André; Cloutier, Guy
2015-08-01
In remote dynamic elastography, the amplitude of the generated displacement field is directly related to the amplitude of the radiation force. Therefore, displacement improvement for better tissue characterization requires the optimization of the radiation force amplitude by increasing the push duration and/or the excitation amplitude applied on the transducer. The main problem of these approaches is that the Food and Drug Administration (FDA) thresholds for medical applications and transducer limitations may be easily exceeded. In the present study, the effect of the frequency used for the generation of the radiation force on the amplitude of the displacement field was investigated. We found that amplitudes of displacements generated by adapted radiation force sequences were greater than those generated by standard nonadapted ones (i.e., single push acoustic radiation force impulse and supersonic shear imaging). Gains in magnitude were between 20 to 158% for in vitro measurements on agar-gelatin phantoms, and 170 to 336% for ex vivo measurements on a human breast sample, depending on focus depths and attenuations of tested samples. The signal-to-noise ratio was also improved more than 4-fold with adapted sequences. We conclude that frequency adaptation is a complementary technique that is efficient for the optimization of displacement amplitudes. This technique can be used safely to optimize the deposited local acoustic energy without increasing the risk of damaging tissues and transducer elements.
Nonlinear frequency mixing in a resonant cavity: numerical simulations in a bubbly liquid.
Vanhille, Christian; Campos-Pozuelo, Cleofé; Sinha, Dipen N
2014-12-01
The study of nonlinear frequency mixing for acoustic standing waves in a resonator cavity is presented. Two high frequencies are mixed in a highly nonlinear bubbly liquid filled cavity that is resonant at the difference frequency. The analysis is carried out through numerical experiments, and both linear and nonlinear regimes are compared. The results show highly efficient generation of the difference frequency at high excitation amplitude. The large acoustic nonlinearity of the bubbly liquid that is responsible for the strong difference-frequency resonance also induces significant enhancement of the parametric frequency mixing effect to generate second harmonic of the difference frequency. PMID:25064635
High frequency nano-optomechanical disk resonators in liquids
Gil-Santos, E; Nguyen, D T; Hease, W; Lemaître, A; Ducci, S; Leo, G; Favero, I
2015-01-01
Vibrating nano- and micromechanical resonators have been the subject of research aiming at ultrasensitive mass sensors for mass spectrometry, chemical analysis and biomedical diagnosis. Unfortunately, their merits diminish dramatically in liquids due to dissipative mechanisms like viscosity and acoustic losses. A push towards faster and lighter miniaturized nanodevices would enable improved performances, provided dissipation was controlled and novel techniques were available to efficiently drive and read-out their minute displacement. Here we report on a nano-optomechanical approach to this problem using miniature semiconductor disks. These devices combine mechanical motion at high frequency above the GHz, ultra-low mass of a few picograms, and moderate dissipation in liquids. We show that high-sensitivity optical measurements allow to direct resolve their thermally driven Brownian vibrations, even in the most dissipative liquids. Thanks to this novel technique, we experimentally, numerically and analytically...
Adaptive optical design in surface plasma resonance sensor
Institute of Scientific and Technical Information of China (English)
ZHANG Feng; ZHONG Jin-gang
2006-01-01
A double-prism adaptive optical design in surface plasma resonance (SPR) sensor is proposed,which consists of two identical isosceles right-triangular prisms. One prism is used as a component of Kretschmann configuration,and the other is for regulation of the optical path. When double-prism structure is angle-scanned by an immovable incident ray,the output ray will be always parallel with the incident ray and just has a small displacement with the shift of output point.The output ray can be focused on a fixed photodetector by a convex lens.Thus it can be avoided that a prism and a photodetector rotate by θ and 2θ respectively in conventional angular scanning SPR sensor.This new design reduces the number of the movable components,makes the structure simple and compact,and makes the manipulation convenient.
Baker, Robert M. L.; Woods, R. Clive; Li, Fangyu
2006-01-01
Here we show the generation of high-frequency-gravitational-waves (HFGWs) utilizing piezoelectric elements such as the ubiquitous Film-Bulk-Acoustic-Resonators (FBARs), found in cell phones, as energized by inexpensive magnetrons, found in microwave ovens, generating GWs having a frequency of about 4.9GHz and their detection by means of new synchro-resonance techniques developed in China. In the 1960s Weber suggested piezoelectric crystals for gravitational-wave (GW) generation. Since then researchers have proposed specific designs. The major obstacle has been the cost of procuring, installing, and energizing a sufficient number of such resonators to generate sufficiently powerful GWs to allow for detection. Recent mass-production techniques, spurred on by the production of cell phones, have driven the cost of resonators down. The new Chinese detector for detecting the 4.9×109Hz HFGW is a coupling-system of fractal membranes-beam-splitters and a narrow, 6.1 cm-radius, pulsed-Gaussian-laser or continuous-Gaussian detection beam passing through a static 15T-magnetic field. The detector is sensitive to GW amplitudes of ~10-30 to be generated with signal-to-noise ratios greater than one. It is concluded that a cost-effective HFGW generation and detection apparatus can now be fabricated and operated in the laboratory. If the two groups or clusters of magnetrons and FBARs were space borne and at lunar distance (e.g., at the Moon and at the lunar L3 libration point) and the quadrupole formalism approximately holds for GW radiators (the FBAR clusters) many GW wavelengths apart, then the HFGW power would be about 420 W and the flux about 2×105 Wm-2 (or more than one hundred times greater than the solar radiation flux at the Earth) focused at the focal spot, or remote-HFGW-emitter, anywhere in the Earth's environs - on or below the Earth's surface.
Re-scaling and adaptive stochastic resonance as a tool for weak GNSS signal acquisition
Institute of Scientific and Technical Information of China (English)
Rongling Lang; Xinyue Li; Fei Gao; Liang Yang
2016-01-01
Weak global navigation satelite system (GNSS) signal acquisition has been a limitation for high sensitivity GPS receivers. This paper modifies the traditional acquisition algorithms and proposes a new weak GNSS signal acquisition method using re-scaling and adaptive stochastic resonance (SR). The adoption of classical SR is limited to low-frequency and periodic signals. Given that GNSS signal frequency is high and that the periodic feature of the GNSS signal is af-fected by the Doppler frequency shift, classical SR methods cannot be directly used to acquire GNSS signals. Therefore, the re-scaling technique is used in our study to expand its usage to high-frequency signals and adaptive control tech-nique is used to gradualy determine the Doppler shift effect in GNSS signal buried in strong noises. The effectiveness of our proposed method was verified by the simulations on GPS L1 signals. The simulation results indicate that the new algorithm based on SR can reach−181 dBW sensitivity with a very short data length of 1 ms.
Measurements of resonance frequencies of clarinet reeds and simulations
Taillard, Pierre-André; Gross, Michel; Dalmont, Jean-Pierre; Kergomard, Jean
2012-01-01
A set of 55 clarinet reeds is observed by holography, collecting 2 series of measurements made under 2 different moisture contents, from which the resonance frequencies of the 15 first modes are deduced. A statistical analysis of the results reveals good correlations, but also significant differences between both series. Within a given series, flexural modes are not strongly correlated. A Principal Component Analysis (PCA) shows that the measurements of each series can be described with 3 factors capturing more than 90% of the variance: the first is linked with transverse modes, the second with flexural modes of high order and the third with the first flexural mode. A forth factor is necessary to take into account the individual sensitivity to moisture content. Numerical 3D simulations are conducted by Finite Element Method, based on a given reed shape and an orthotropic model. A sensitivity analysis revels that, besides the density, the theoretical frequencies depend mainly on 2 parameters: $E_L$ and $G_{LT}...
Institute of Scientific and Technical Information of China (English)
ZHANG Hui; ZHANG Shu-Yi; FAN Li
2009-01-01
A model of high-overtone bulk acoustic resonators is used to study the effects of thickness deviation of elastic plates on resonance frequency spectra in planar multi-layered systems. The resonance frequency shifts induced by the thickness deviations of the elastic plates periodically vary with the resonance order, which depends on the acoustic impedance ratios of the elastic plates to piezoelectric patches. Additionally, the center lines of the frequency shift oscillations Hnearly change with the orders of the resonance modes, and their slopes are sensitive to the thickness deviations of the plates, which can be used to quantitatively evaluate the thickness deviations.
DEFF Research Database (Denmark)
Tang, Yi; Yao, Wenli; Loh, Poh Chiang;
2016-01-01
This paper proposes a novel LCL filter design method and its current control for grid-connected converters. With the proposed design method, it is possible to set the resonance frequency of the LCL filter to be higher than the Nyquist frequency, i.e., half of the system sampling frequency...
Resonant frequencies of massless scalar field in rotating black-brane spacetime
Institute of Scientific and Technical Information of China (English)
Jing Ji-Liang; Pan Qi-Yuan
2008-01-01
This paper investigates the resonant frequencies of the massless scalar field in the near extremal Kerr-like black-brahe spacetime. It is shown that the different angular quantum number will present different resonant frequencies. It is also shown that the real part of the resonant frequencies increases as the compact dimensions parameter μi increases, but the magnitude of the imaginary part decreases as μi increases.
DEFF Research Database (Denmark)
Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede
2015-01-01
(PR) and Repetitive Controllers (RC). The synchronization is actually to detect the instantaneous grid information (e.g., frequency and phase of the grid voltage) for the current control, which is commonly performed by a Phase-Locked-Loop (PLL) system. As a consequence, harmonics and deviations......It is mandatory for grid-connected power converters to synchronize the feed-in currents with the grid. Moreover, the power converters should produce feed-in currents with low total harmonic distortions according to the demands, by employing advanced current controllers, e.g., Proportional Resonant...... deviations. Experiments on a single-phase grid-connected inverter system are presented, which have verified the proposals and also the effectiveness of the frequency adaptive current controllers....
International Nuclear Information System (INIS)
A fast full-wave numerical approach was developed for simulating high-field multi-channel radio-frequency (RF) receive coil arrays in magnetic resonance imaging. To improve the efficiency, the impedance matrix was compressed by a multilevel adaptive cross approximation method. Furthermore, careful organization of multiple coil simulations was applied so that the impedance matrix associated with biological subjects is constructed and pre-conditioned only once. Numerical examples demonstrate the efficacy of the proposed approach for RF coil simulations.
Quantum dot admittance probed at microwave frequencies with an on-chip resonator
Frey, T.; Leek, P. J.; Beck, M.; Faist, J.; Wallraff, A.; Ensslin, K.; Ihn, T.; Büttiker, M.
2012-09-01
We present microwave frequency measurements of the dynamic admittance of a quantum dot tunnel-coupled to a two-dimensional electron gas. The measurements are made via a high-quality 6.75 GHz on-chip resonator capacitively coupled to the dot. The resonator frequency is found to shift both down and up close to conductance resonance of the dot corresponding to a change of sign of the reactance of the system from capacitive to inductive. The observations are consistent with a scattering matrix model. The sign of the reactance depends on the detuning of the dot from conductance resonance and on the magnitude of the tunnel rate to the lead with respect to the resonator frequency. Inductive response is observed on a conductance resonance when tunnel coupling and temperature are sufficiently small compared to the resonator frequency.
DEFF Research Database (Denmark)
Tang, Meng; Cagliani, Alberto; Escouflaire, Marie;
2010-01-01
A bulk disk resonator working in dynamic mode is used for mass detection. In the capacitive transduction scheme, the parasitic capacitance between the electrodes produces an anti resonance in the transmission curve, which distorts the phase shift at the resonant frequency and increases the freque......A bulk disk resonator working in dynamic mode is used for mass detection. In the capacitive transduction scheme, the parasitic capacitance between the electrodes produces an anti resonance in the transmission curve, which distorts the phase shift at the resonant frequency and increases...... the frequency noise of the system. A capacitor cancellation circuit is used to subtract the parasitic capacitor. Measurements are conducted before and after the cancellation, and results show that after cancellation, the anti resonance is suppressed and the frequency noise is decreased, thus decreasing...
Signal Adaptive System for Space/Spatial-Frequency Analysis
Directory of Open Access Journals (Sweden)
Veselin N. Ivanović
2009-01-01
Full Text Available This paper outlines the development of a multiple-clock-cycle implementation (MCI of a signal adaptive two-dimensional (2D system for space/spatial-frequency (S/SF signal analysis. The design is based on a method for improved S/SF representation of the analyzed 2D signals, also proposed here. The proposed MCI design optimizes critical design performances related to hardware complexity, making it a suitable system for real time implementation on an integrated chip. Additionally, the design allows the implemented system to take a variable number of clock cycles (CLKs (the only necessary ones regarding desirable—2D Wigner distribution-presentation of autoterms in different frequency-frequency points during the execution. This ability represents a major advantage of the proposed design which helps to optimize the time required for execution and produce an improved, cross-terms-free S/SF signal representation. The design has been verified by a field-programmable gate array (FPGA circuit design, capable of performing S/SF analysis of 2D signals in real time.
Damelin, S. B.; Y. Gu; Wunsch II, D. C.; Xu, R
2014-01-01
In this paper, we describe an algorithm FARDiff (Fuzzy Adaptive Resonance Dif- fusion) which combines Diffusion Maps and Fuzzy Adaptive Resonance Theory to do clustering on high dimensional data. We describe some applications of this method and some problems for future research.
Savchenkov, Anatoliy A. (Inventor); Strekalov, Dmitry V. (Inventor); Maleki, Lute (Inventor); Matsko, Andrey B. (Inventor); Iltchenko, Vladimir S. (Inventor); Martin, Jan M. (Inventor)
2010-01-01
A method of shifting and fixing an optical frequency of an optical resonator to a desired optical frequency, and an optical resonator made by such a method are provided. The method includes providing an optical resonator having a surface and a refractive index, and obtaining a coating composition having a predetermined concentration of a substance and having a refractive index that is substantially similar to the refractive index of the optical resonator. The coating composition inherently possesses a thickness when it is applied as a coating. The method further includes determining a coating ratio for the surface of the optical resonator and applying the coating composition onto a portion of the surface of the optical resonator based upon the determined coating ratio.
Lee, Jungshin; Rhim, Jaewook
2012-09-01
Differential vibrating accelerometer (DVA) is a resonant-type sensor which detects the change in the resonant frequency in the presence of acceleration input, i.e. inertial loading. However, the resonant frequency of micromachined silicon resonators is sensitive to the temperature change as well as the input acceleration. Therefore, to design a high-precision vibrating accelerometer, the temperature sensitivity of the resonant frequency has to be predicted and compensated accurately. In this study, a temperature compensation method for resonant frequency is proposed which controls the electrostatic stiffness of the dual-ended tuning fork (DETF) using the temperature-dependent dc voltage between the parallel plate electrodes. To do this, the electromechanical model is derived first to predict the change in the electrostatic stiffness and the resonant frequency resulting from the dc voltage between the resonator and the electrodes. Next, the temperature sensitivity of the resonant frequency is modeled, estimated and compared with the measured values. Then it is shown that the resonant frequency of the DETF can be kept constant in the operating temperature range by applying the temperature-dependent driving voltage to the parallel plate electrodes. The proposed method is validated through experiment.
International Nuclear Information System (INIS)
Differential vibrating accelerometer (DVA) is a resonant-type sensor which detects the change in the resonant frequency in the presence of acceleration input, i.e. inertial loading. However, the resonant frequency of micromachined silicon resonators is sensitive to the temperature change as well as the input acceleration. Therefore, to design a high-precision vibrating accelerometer, the temperature sensitivity of the resonant frequency has to be predicted and compensated accurately. In this study, a temperature compensation method for resonant frequency is proposed which controls the electrostatic stiffness of the dual-ended tuning fork (DETF) using the temperature-dependent dc voltage between the parallel plate electrodes. To do this, the electromechanical model is derived first to predict the change in the electrostatic stiffness and the resonant frequency resulting from the dc voltage between the resonator and the electrodes. Next, the temperature sensitivity of the resonant frequency is modeled, estimated and compared with the measured values. Then it is shown that the resonant frequency of the DETF can be kept constant in the operating temperature range by applying the temperature-dependent driving voltage to the parallel plate electrodes. The proposed method is validated through experiment. (paper)
Nanoscale Subsurface Imaging via Resonant Difference-Frequency Atomic Force Ultrasonic Microscopy
Cantrell, Sean A.; Cantrell, John H.; Lilehei, Peter T.
2007-01-01
A novel scanning probe microscope methodology has been developed that employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by the fundamental resonance frequency of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever fundamental resonance. The resonance-enhanced difference-frequency signals are used to create images of embedded nanoscale features.
Using genetic algorithm based fuzzy adaptive resonance theory for clustering analysis
Institute of Scientific and Technical Information of China (English)
LIU Bo; WANG Yong; WANG Hong-jian
2006-01-01
In the clustering applications field, fuzzy adaptive resonance theory system has been widely applied. But, three parameters of fuzzy adaptive resonance theory need to be adjusted manually for obtaining better clustering. It needs much time to test and does not assure a best result. Genetic algorithm is an optimal mathematical search technique based on the principles of natural selection and genetic recombination. So, to make the fuzzy adaptive resonance theory parameters choosing process automation, an approach incorporating genetic algorithm and fuzzy adaptive resonance theory neural network has been applied. Then, the best clustering result can be obtained.Through experiment, it can be proved that the most appropriate parameters of fuzzy adaptive resonance theory can be gained effectively by this approach.
Chembo, Yanne K.; Baumgartel, Lukas; Grudinin, Ivan; Strekalov, Dmitry; Thompson, Robert; Yu, Nan
2012-01-01
Whispering gallery mode resonators are attracting increasing interest as promising frequency reference cavities. Unlike commonly used Fabry-Perot cavities, however, they are filled with a bulk medium whose properties have a significant impact on the stability of its resonance frequencies. In this context that has to be reduced to a minimum. On the other hand, a small monolithic resonator provides opportunity for better stability against vibration and acceleration. this feature is essential when the cavity operates in a non-laboratory environment. In this paper, we report a case study for a crystalline resonator, and discuss the a pathway towards the inhibition of vibration-and acceleration-induced frequency fluctuations.
Successive Resonances for Ion Ejection at Arbitrary Frequencies in an Ion Trap
Snyder, Dalton T.; Cooks, R. Graham
2016-09-01
The use of successive resonances for ion ejection is demonstrated here as a method of scanning quadrupole ion traps with improvement in both resolution and sensitivity compared with single frequency resonance ejection. The conventional single frequency resonance ejection waveform is replaced with a dual-frequency waveform. The two included frequencies are spaced very closely and their relative amplitudes are adjusted so that the first frequency that ions encounter excites them to higher amplitudes where space charge effects are less prominent, thereby giving faster and more efficient ejection when the ions come into resonance with the second frequency. The method is applicable at any arbitrary frequency, unlike double and triple resonance methods. However, like double and triple resonance ejection, ejection using successive resonances requires the rf and AC waveforms to be phase-locked in order to retain mass accuracy and mass precision. The improved performance is seen in mass spectra acquired by rf amplitude scans (resonance ejection) as well as by secular frequency scans.
Waveguide-type optical passive ring resonator gyro using frequency modulation spectroscopy technique
Liang, Ning; Lijun, Guo; Mei, Kong; Tuoyuan, Chen
2014-12-01
This paper reports the experimental results of silica on a silicon ring resonator in a resonator micro optic gyroscope based on the frequency modulation spectroscopy technique by our research group. The ring resonator is composed of a 4 cm diameter silica waveguide. By testing at λ = 1550 nm, the FSR, FWHM and the depth of resonance are 3122 MHz, 103.07 MHz and 0.8 respectively. By using a polarization controller, the resonance curve under the TM mode can be inhibited. The depth of resonance increased from 0.8 to 0.8913, namely the finesse increase from 30.33 to 33.05. In the experiments, there is an acoustic-optical frequency shifter (AOFS) in each light loop. We lock the lasing frequency at the resonance frequency of the silica waveguide ring resonator for the counterclockwise lightwave; the frequency difference between the driving frequencies of the two AOFS is equivalent to the Sagnac frequency difference caused by gyro rotation. Thus, the gyro output is observed. The slope of the linear fit is about 0.330 mV/(°/s) based on the -900 to 900 kHz equivalent frequency and the gyro dynamic range is ±2.0 × 103 rad/s.
Luthy, Sarah K; Marinkovic, Aleksandar; Weiner, Daniel J
2011-06-01
High-frequency chest compression (HFCC) is a therapy for cystic fibrosis (CF). We hypothesized that the resonant frequency (f(res)), as measured by impulse oscillometry, could be used to determine what HFCC vest settings produce maximal airflow or volume in pediatric CF patients. In 45 subjects, we studied: f(res), HFCC vest frequencies that subjects used (f(used)), and the HFCC vest frequencies that generated the greatest volume (f(vol)) and airflow (f(flow)) changes as measured by pneumotachometer. Median f(used) for 32 subjects was 14 Hz (range, 6-30). The rank order of the three most common f(used) was 15 Hz (28%) and 12 Hz (21%); three frequencies tied for third: 10, 11, and 14 Hz (5% each). Median f(res) for 43 subjects was 20.30 Hz (range, 7.85-33.65). Nineteen subjects underwent vest-tuning to determine f(vol) and f(flow). Median f(vol) was 8 Hz (range, 6-30). The rank order of the three most common f(vol) was: 8 Hz (42%), 6 Hz (32%), and 10 Hz (21%). Median f(flow) was 26 Hz (range, 8-30). The rank order of the three most common f(flow) was: 30 Hz (26%) and 28 Hz (21%); three frequencies tied for third: 8, 14, and 18 Hz (11% each). There was no correlation between f(used) and f(flow) (r(2) = -0.12) or f(vol) (r(2) = 0.031). There was no correlation between f(res) and f(flow) (r(2) = 0.19) or f(vol) (r(2) = 0.023). Multivariable analysis showed no independent variables were predictive of f(flow) or f(vol). Vest-tuning may be required to optimize clinical utility of HFCC. Multiple HFCC frequencies may need to be used to incorporate f(flow) and f(vol).
Stress adaptation and low-frequency impedance of rat lungs.
Peslin, R; Duvivier, C; Bekkari, H; Reichart, E; Gallina, C
1990-09-01
At transpulmonary pressures (Ptp) of 7-12 cmH2O, pressure-volume hysteresis of isolated cat lungs has been found to be 20-50% larger than predicted from their amount of stress adaptation (J. Hildebrandt, J. Appl. Physiol. 28: 365-372, 1970). This behavior is inconsistent with linear viscoelasticity and has been interpreted in terms of plastoelasticity. We have reinvestigated this phenomenon in isolated lungs from 12 Wistar rats by measuring 1) the changes in Ptp after 0.5-ml step volume changes (initial Ptp of 5 cmH2O) and 2) their response to sinusoidal pressure forcing from 0.01 to 0.67 Hz (2 cmH2O peak to peak, mean Ptp of 6 cmH2O). Stress adaptation curves were found to fit approximately Hildebrandt's logarithmic model [delta Ptp/delta V = A - B.log(t)] from 0.2 to 100 s, where delta V is the step volume change, A and B are coefficients, and t is time. A and B averaged 1.06 +/- 0.11 and 0.173 +/- 0.019 cmH2O/ml, respectively, with minor differences between stress relaxation and stress recovery curves. The response to sinusoidal forcing was characterized by the effective resistance (Re) and elastance (EL). Re decreased from 2.48 +/- 0.41 cmH2O.ml-1.s at 0.01 Hz to 0.18 +/- 0.03 cmH2O.ml-1.s at 0.5 Hz, and EL increased from 0.99 +/- 0.10 to 1.26 +/- 0.20 cmH2O/ml on the same frequency range. These data were analyzed with the frequency-domain version of the same model, complemented by a Newtonian resistance (R) to account for airway resistance: Re = R + B/ (9.2f) and EL = A + 0.25B + B . log 2 pi f, where f is the frequency.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2246156
Frequency Characteristics of Double-Walled Carbon Nanotube Resonator with Different Length
Jun-Ha LEE; Jeong-Won KANG; Kim, Jin-Tae
2016-01-01
In this paper, we have conducted classical molecular dynamics simulations for DWCNTs of various wall lengths to investigate their use as ultrahigh frequency nano-mechanical resonators. We sought to determine the variations in the frequency of these resonators according to changes in the DWCNT wall lengths. For a double-walled carbon nanotube resonator with a shorter inner nanotube, the shorter inner nanotube can be considered to be a flexible core, and thus, the length influences the fundamen...
Mechanically Tunable Dielectric Resonator Metasurfaces at Visible Frequencies.
Gutruf, Philipp; Zou, Chengjun; Withayachumnankul, Withawat; Bhaskaran, Madhu; Sriram, Sharath; Fumeaux, Christophe
2016-01-26
Devices that manipulate light represent the future of information processing. Flat optics and structures with subwavelength periodic features (metasurfaces) provide compact and efficient solutions. The key bottleneck is efficiency, and replacing metallic resonators with dielectric resonators has been shown to significantly enhance performance. To extend the functionalities of dielectric metasurfaces to real-world optical applications, the ability to tune their properties becomes important. In this article, we present a mechanically tunable all-dielectric metasurface. This is composed of an array of dielectric resonators embedded in an elastomeric matrix. The optical response of the structure under a uniaxial strain is analyzed by mechanical-electromagnetic co-simulations. It is experimentally demonstrated that the metasurface exhibits remarkable resonance shifts. Analysis using a Lagrangian model reveals that strain modulates the near-field mutual interaction between resonant dielectric elements. The ability to control and alter inter-resonator coupling will position dielectric metasurfaces as functional elements of reconfigurable optical devices. PMID:26617198
Analysis of a shielded TE011 mode composite dielectric resonator for stable frequency reference
Indian Academy of Sciences (India)
N D Kataria; K S Daya; V G Das
2002-05-01
Analysis of a TE011 mode composite sapphire–rutile dielectric resonator has been carried out to study the temperature variation of resonance frequency, close to the Cs atomic clock hyperﬁne frequency of 9.192 GHz. The complementary behavior of dielectric permittivity with temperature of the composite has been exploited to obtain the desired turning point in the resonant frequency. The frequency of the composite structure is found to be independent of the shield diameter beyond four times the puck diameter.
Sub-wavelength resonant structures at microwave and optical frequencies
Simić, Aleksandar
2011-01-01
Sub-wavelength scale resonant structures have been at the forefront of physics and engineering in the past decade. They offer a path for creation of new materials and great advancements in the field of photonics. This dissertation deals with design, fabrication and characterization of sub -wavelength resonant structures. In the first part, we investigate the application of passive sub-wavelength resonators in meta-materials --- materials that have electromagnetic properties otherwise unattain...
Resonance Analysis of High-Frequency Electrohydraulic Exciter Controlled by 2D Valve
Directory of Open Access Journals (Sweden)
Guojun Pan
2015-01-01
Full Text Available The resonant characteristic of hydraulic system has not been described yet because it is necessarily restricted by linear assumptions in classical fluid theory. A way of the resonance analysis is presented for an electrohydraulic exciter controlled by 2D valve. The block diagram of this excitation system is established by extracting nonlinear parts from the traditional linearization analysis; as a result the resonant frequency is obtained. According to input energy from oil source which is equal to the reverse energy to oil source, load pressure and load flow are solved analytically as the working frequency reaches the natural frequency. The analytical expression of resonant peak is also derived without damping. Finally, the experimental system is built to verify the theoretical analysis. The initial research on resonant characteristic will lay theoretical foundation and make useful complement for resonance phenomena of classical fluid theory in hydraulic system.
Wavelet-Based Speech Enhancement Using Time-Frequency Adaptation
Directory of Open Access Journals (Sweden)
Kun-Ching Wang
2009-01-01
Full Text Available Wavelet denoising is commonly used for speech enhancement because of the simplicity of its implementation. However, the conventional methods generate the presence of musical residual noise while thresholding the background noise. The unvoiced components of speech are often eliminated from this method. In this paper, a novel algorithm of wavelet coefficient threshold (WCT based on time-frequency adaptation is proposed. In addition, an unvoiced speech enhancement algorithm is also integrated into the system to improve the intelligibility of speech. The wavelet coefficient threshold (WCT of each subband is first temporally adjusted according to the value of a posterior signal-to-noise ratio (SNR. To prevent the degradation of unvoiced sounds during noise, the algorithm utilizes a simple speech/noise detector (SND and further divides speech signal into unvoiced and voiced sounds. Then, we apply appropriate wavelet thresholding according to voiced/unvoiced (V/U decision. Based on the masking properties of human auditory system, a perceptual gain factor is adopted into wavelet thresholding for suppressing musical residual noise. Simulation results show that the proposed method is capable of reducing noise with little speech degradation and the overall performance is superior to several competitive methods.
Adaptive multimode signal reconstruction from time-frequency representations.
Meignen, Sylvain; Oberlin, Thomas; Depalle, Philippe; Flandrin, Patrick; McLaughlin, Stephen
2016-04-13
This paper discusses methods for the adaptive reconstruction of the modes of multicomponent AM-FM signals by their time-frequency (TF) representation derived from their short-time Fourier transform (STFT). The STFT of an AM-FM component or mode spreads the information relative to that mode in the TF plane around curves commonly called ridges. An alternative view is to consider a mode as a particular TF domain termed a basin of attraction. Here we discuss two new approaches to mode reconstruction. The first determines the ridge associated with a mode by considering the location where the direction of the reassignment vector sharply changes, the technique used to determine the basin of attraction being directly derived from that used for ridge extraction. A second uses the fact that the STFT of a signal is fully characterized by its zeros (and then the particular distribution of these zeros for Gaussian noise) to deduce an algorithm to compute the mode domains. For both techniques, mode reconstruction is then carried out by simply integrating the information inside these basins of attraction or domains. PMID:26953184
Institute of Scientific and Technical Information of China (English)
Zhang Ling-Ying; Jin Guo-Xiang; Cao Li; Wang Zhi-Yun
2012-01-01
Considering a damped linear oscillator model subjected to a white noise with an inherent angular frequency and a periodic external driving force,we derive the analytic expression of the first moment of output response,and study the stochastic resonance phenomenon in a system.The results show that the output response of this system behaves as a simple harmonic vibration,of which the frequency is the same as the external driving frequency,and the variations of amplitude with the driving frequency and the inherent frequency present a bona fide stochastic resonance.
Multi-frequency resonator based on dual-band S-shaped left-handed material.
Wang, Dongxing; Ran, Lixin; Wu, Bae-Ian; Chen, Hongsheng; Huangfu, Jiangtao; Grzegorczyk, Tomasz M; Kong, J A
2006-12-11
In this paper, we experimentally realize a one-dimensional RHM (Right-handed Material)-LHM (Left-handed Material) multi-frequency resonator that consists of a dual-negative-band LHM and air arranged in an X-band waveguide. Multi-resonant frequencies are observed within two left-handed bands of the LHM. The effects of the loss and the hyperbolic dispersion relation of LHM layer are discussed. The incorporation of such a LHM into the resonator design allows more flexibility to realize multi-resonance. PMID:19529656
Frequency Characteristics of Double-Walled Carbon Nanotube Resonator with Different Length
Directory of Open Access Journals (Sweden)
Jun-Ha LEE
2016-05-01
Full Text Available In this paper, we have conducted classical molecular dynamics simulations for DWCNTs of various wall lengths to investigate their use as ultrahigh frequency nano-mechanical resonators. We sought to determine the variations in the frequency of these resonators according to changes in the DWCNT wall lengths. For a double-walled carbon nanotube resonator with a shorter inner nanotube, the shorter inner nanotube can be considered to be a flexible core, and thus, the length influences the fundamental frequency. In this paper, we analyze the variation in frequency of ultra-high frequency nano-mechnical resonators constructed from DWCNTs with different wall lengths.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12951
On the frequency and field linewidth conversion of ferromagnetic resonance spectra
International Nuclear Information System (INIS)
Both frequency swept and field swept ferromagnetic resonance measurements have been carried out for a number of different samples with negligible, moderate and significant extrinsic frequency independent linewidth contribution to analyze the correlation between the experimentally measured frequency and field linewidths. Contrary to the belief commonly held by many researchers, it is found that the frequency and field linewidth conversion relation does not hold for all cases. Instead it holds only for samples with negligible frequency independent linewidth contributions. For samples with non-negligible frequency independent linewidth contribution, the field linewidth values converted from the measured frequency linewidth are larger than the experimentally measured field linewidth. A close examination of the literature reveals that previously reported results support our findings, with successful conversions related to samples with negligible frequency independent linewidth contributions and unsuccessful conversions related to samples with significant frequency independent linewidth. The findings are important in providing guidance in ferromagnetic resonance linewidth conversions. (paper)
Low-frequency tunable acoustic absorber based on split tube resonators
Wu, Xiaoxiao; Fu, Caixing; Li, Xin; Meng, Yan; Gao, Yibo; Tian, Jingxuan; Wang, Li; Huang, Yingzhou; Yang, Zhiyu; Wen, Weijia
2016-07-01
We demonstrate a high-efficiency tunable acoustic absorber for low frequencies (acoustic absorber is based on split tube resonators and could reach high-efficiency absorption at tunable resonance frequency with wavelength in air at least 30 times larger than its total thickness in simulations and experiments. The resonance frequency and high-efficiency absorption of the absorber are robust under oblique incidence even at large angles. The absorber could have potential applications for acoustic engineering due to its high structural stability, ease of fabrication, subwavelength thickness, and robust high-efficiency.
Mechanical design of RFQ resonator cavities in the 400-MHz frequency range
International Nuclear Information System (INIS)
Many RFQ resonator-cavity design concepts have been proposed in the 400-MHz frequency range. Los Alamos has been evaluating RFQ resonator-cavity designs that provide acceptable combinations of necessary mechanical features, easy tunability and long-term stability. Four RFQ resonator test cavities have been fabricated to test rf joints between the RFQ vanes and the resonator cavity. Two of these joints (the C-seal and the rf clamp-joint) allow vane movement for tuning. These test data, and the design of the present generation of RFQ resonator cavities, are presented
External Ear Resonant Amplitude and Frequency of 3-7 Year Old Children
Directory of Open Access Journals (Sweden)
Amir Hossein Zare
2004-06-01
Full Text Available Objective: To measure external ear resonant amplitude and frequency in children (3-7 years old and to compare with adult measures. Method and materials: The external ear resonance peak amplitude and frequency of 63 children 3-7 years old were recorded. All of the children had normal tympanogram and there was no cerumen in external auditory canal. 20 adult of 21-24 years old (10 male , 10 female were selected in order to compare with children that had normal tympanogram. The tests included : 1-otoscopy 2- tympanometry 3-microphone probe tube test. Results: The average of resonance peak frequency for children and adult is 4200 Hz and 3200 Hz , respectively. The resonance frequency of children had significantly diffrence with average of resonance frequency in adults. The average of resonance peak amplitude for children and adult is 17.70 dB and 17.17 dB , respectively. Conclusion: Resonant frequency and amplitude affect the hearing aid prescription and fitting process and calculating insertion gain; so, this measures seem should be considered in children hearing aid fitting.
Radiation-induced frequency transients in AT, BT, and SC cut quartz resonators
International Nuclear Information System (INIS)
Earlier studies of transient frequency changes in high-purity swept AT quartz resonators led to the conclusion that impurity-induced effects were small, while the observed changes were qualitatively and quantitatively well characterized in terms of the time changing temperature of the vibrating quartz and its effect on frequency. 5 MHz, AT cut fifth overtone, and BT and SC cut third overtone resonators were prepared from a single stone of Sawyer swept Premium-Q quartz. The resonators were operated in precision ovenized oscillators at or near their turnover temperatures. Pulsed irradiation, at dose levels of the order of 104 rads (Si) per pulse, was accomplished at Sandia. The experimental data display negative frequency transients for the AT cut resonators, positive frequency transients for the BT cut resonators, and very small transient effects for the SC cut resonators. From these experimental results, it is concluded that no measurable impurity-induced frequency changes are observed in this high-purity swept-quartz and that the frequency transients are accurately modelled in terms of transient temperature effects stemming from the thermal characteristics of the resonator structure
Resonance frequency control for the KOMAC 100-MeV drift tube linac
Kwon, Hyeok-Jung
2015-02-01
A 100-MeV proton accelerator has been developed, and the operation and beam service started at the Korea Multi-purpose Accelerator Complex (KOMAC) in July 2013. The accelerator consists of a 50-keV proton injector, a 3-MeV radio-frequency quadrupole (RFQ) and a 100-MeV drift tube linac (DTL). The resonance frequencies of the DTL tanks are controlled by using the resonance frequency control cooling system (RCCS), installed at every DTL tank. Until now, the RCCS has been operating in the constant temperature mode. If the system is to be stabilized better, the RCCS must be operated in the frequency control mode. For this purpose, studies, including the relation between the resonance frequency and RCCS operation temperature, were done under various conditions. In this paper, the preparations for the frequency control loop of the RCCS are described.
Ultra-Narrow Bandwidth Optical Resonators for Integrated Low Frequency Noise Lasers
Spencer, Daryl T.
The development of narrowband resonators has far reaching applications in integrated optics. As a precise reference of wavelength, filters can be used in sensors, metrology, nonlinear optics, microwave photonics, and laser stabilization. In this work, we develop record high quality factor (Q) Si 3N4 waveguide resonators, and utilize them to stabilize a heterogeneously integrated Si/III V laser. To increase the Q factor of waveguide resonators, particular attention is given to loss mechanisms. Propagation loss of filtering is performed with Si resonant mirrors in the laser cavity. A 30 million Q factor Si3N4 resonator is used with electrical feedback to reduce close in noise and frequency walk off. The laser shows high frequency noise levels of 60x103 Hz2/Hz corresponding to 160 kHz linewidth, and the low frequency noise is suppressed 33 dB to 103 Hz2/Hz with the PDH system.
Nordquist, Christopher D.; Branch, Darren W.; Pluym, Tammy; Choi, Sukwon; Nguyen, Janet H.; Grine, Alejandro; Dyck, Christopher W.; Scott, Sean M.; Sing, Molly N.; Olsson, Roy H., III
2016-10-01
Switching of transducer coupling in aluminum nitride contour-mode resonators provides an enabling technology for future tunable and reconfigurable filters for multi-function RF systems. By using microelectromechanical capacitive switches to realize the transducer electrode fingers, coupling between the metal electrode finger and the piezoelectric material is modulated to change the response of the device. On/off switched width extensional resonators with an area of 24 dB switching ratio at a resonator center frequency of 635 MHz. Other device examples include a 63 MHz resonator with switchable impedance and a 470 MHz resonator with 127 kHz of fine center frequency tuning accomplished by mass loading of the resonator with the MEMS switches.
The characteristics of plasma-sheath resonances in a non-uniform radio-frequency plasma
International Nuclear Information System (INIS)
Plasma-sheath resonances in the resonance-probe were first reported by Takayama et al. in 1960. At that time the resonance was thought to occur at the plasma frequency; later work, however, showed that a plasma-sheath resonance was taking place. In this paper the authors plotted the ratio of RF field in the probe sheath to the RF probe voltage versus ω/ωep, and found that the ratio passed through a maximum when the probe was at resonance. The maximum corresponded to a ratio ω/ωep less than 1, the resonance frequency was confirmed to be below the plasma frequency and the open-quotes series resonance modelclose quotes was verified. After this definitive paper on the subject the interest of resonance probe moved into more practical applications. These include: determining the collision frequency between the electrons and neutrals in a low density plasma; measuring the electron density in the ionosphere; measuring the averaged densities of the charged particles as well as their temperature in a bounded plasma with an external magnetic field; studying antenna signals in space plasmas, etc. It is apparent that the harmonics developing in the plasma may weaken the conventional open-quotes drivenclose quotes Langmuir probe technique which is widely used in plasma research. There have been many attempts to resolve this problem, for example, driving, actively, the first two RF harmonics that appear across the probe sheath to achieve more precise plasma parameters. Nevertheless, it has been recently found that the natural frequency of the plasma-sheath system can be much more influential than the contributions from the external circuitry at certain fairly low pressures. This in particular when the plasma-sheath resonance coincides with one of the harmonics of the fundamental frequency. In this contribution we present some theoretical and experimental aspects of the plasma-sheath resonance in a parallel-plate RF plasma reactor
Single-Chip Multiple-Frequency RF MEMS Resonant Platform for Wireless Communications Project
National Aeronautics and Space Administration — A novel, single-chip, multiple-frequency platform for RF/IF filtering and clock reference based on contour-mode aluminum nitride (AlN) MEMS piezoelectric resonators...
Frequency Coded Chipless RFID Tag using Spurline Resonators
Sumi, M.; Dinesh, R.; C. M. Nijas; Mridula, S.; P. Mohanan
2014-01-01
A novel compact chipless RFID tag using spurline resonators is discussed in this paper. The detection of the tag's ID is using the spectral signature of a spurline resonator circuit. The tag has a data capacity of 8-bits in the range 2.38 to 4.04 GHz. The tag consists of a spurline multiresonating circuit and two cross polarised antennas. The prototype of the tag is fabricated on a substrate C-MET/LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. The measured results show that group ...
Resonance frequencies of a cavity containing a compressible viscous fluid
Conca, C.; Planchard, J.; Vanninathan, M.
1993-03-01
The aim of this paper is to study the resonance spectrum of a cavity containing a compressible viscous fluid. This system admits a discrete infinite sequence of eigenvalues whose real parts are negative, which is interpreted as the damping effect introduced by viscosity. Only a finite number of them have non-zero imaginary parts and this number depends on viscosity; a simple criterion is given for their position in the complex plane. The case of a cavity containing an elastic mechanical system immersed in the fluid is also examined; from a qualitative point of view, the nature of the resonance spectrum remains unchanged.
My, Thu-Hien; Drag, Cyril; Bretenaker, Fabien
2008-07-01
A widely tunable continuous intracavity-frequency-doubled singly resonant optical parametric oscillator based on MgO-doped periodically poled stoichiometric lithium tantalate crystal is described. The idler radiation resonating in the cavity is frequency doubled by an intracavity BBO crystal. Pumped in the green, this system can provide up to 485 mW of single-frequency orange radiation. The system is continuously temperature tunable between 1170 and 1355 nm for the idler, 876 and 975 nm for the signal, and between 585 and 678 nm for the doubled idler. The free-running power and frequency stability of the system have been observed to be better than those for a single-mode dye laser.
My, Thu-Hien; Drag, Cyril; Bretenaker, Fabien
2008-07-01
A widely tunable continuous intracavity-frequency-doubled singly resonant optical parametric oscillator based on MgO-doped periodically poled stoichiometric lithium tantalate crystal is described. The idler radiation resonating in the cavity is frequency doubled by an intracavity BBO crystal. Pumped in the green, this system can provide up to 485 mW of single-frequency orange radiation. The system is continuously temperature tunable between 1170 and 1355 nm for the idler, 876 and 975 nm for the signal, and between 585 and 678 nm for the doubled idler. The free-running power and frequency stability of the system have been observed to be better than those for a single-mode dye laser. PMID:18594663
Dark resonances in the field of frequency shifted feedback laser radiation
Romanenko, V. I.; Romanenko, A. V.; Yatsenko, L. P.; Kazakov, G. A.; Litvinov, A. N.; Matisov, B. G.; Rozhdestvensky, Yu. V.
2010-01-01
We present a theory of dark resonances in a fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency shifted feedback (FSF) laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulses train. We study analytically the field broadening and the light shift of the resonances.
Dark resonances in the field of frequency-shifted feedback laser radiation
Romanenko, V. I.; Romanenko, A. V.; Yatsenko, L. P.; Kazakov, G. A.; Litvinov, A. N.; Matisov, B. G.; Rozhdestvensky, Yu V.
2010-11-01
We present a theory of dark resonances in fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency-shifted feedback laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulse train. We study analytically the field broadening and the light shift of the resonances.
Dark resonances in the field of frequency-shifted feedback laser radiation
International Nuclear Information System (INIS)
We present a theory of dark resonances in fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency-shifted feedback laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulse train. We study analytically the field broadening and the light shift of the resonances.
Dark resonances in the field of frequency-shifted feedback laser radiation
Energy Technology Data Exchange (ETDEWEB)
Romanenko, V I; Romanenko, A V; Yatsenko, L P [Institute of Physics, National Academy of Science of Ukraine, 46, Nauky Avenue, Kyiv 03028 (Ukraine); Kazakov, G A; Litvinov, A N; Matisov, B G [St Petersburg State Polytechnical University, 29, Polytechnicheskaya st, St. Petersburg 195251 (Russian Federation); Rozhdestvensky, Yu V, E-mail: vr@iop.kiev.u, E-mail: andrey.litvinov@mail.r [S I Vavilov State Optical Institute 12, Birzhevaya Liniya st, St Petersburg 199034 (Russian Federation)
2010-11-14
We present a theory of dark resonances in fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency-shifted feedback laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulse train. We study analytically the field broadening and the light shift of the resonances.
Energy Technology Data Exchange (ETDEWEB)
Ohta, N; Niki, T; Kirihara, S, E-mail: n-ohta@jwri.osaka-u.ac.jp [Smart Processing Research Center, Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka, 567-0047 (Japan)
2011-05-15
Terahertz wave resonators composed of alumina photonic crystals with diamond lattice structures were designed and fabricated by using micro stereolithography. These three dimensional periodic structures can reflect perfectly electromagnetic waves through Bragg diffraction. A micro glass cell including water solutions was put between the photonic crystals as a novel resonance sensor with terahertz frequency range. The localized and amplified waves in the resonators were measured by a spectroscopy, and visualized by theoretical simulations.
Directory of Open Access Journals (Sweden)
Jami Rajesh
2014-02-01
Full Text Available This paper deals with a novel type soft switching utility frequency AC- high frequency AC converter using asymmetrical PWM bidirectional active switches which can be defined as high frequency resonant matrix converter.This power frequency changer can directly convert utility frequency AC power to high frequency AC power ranging more than 20kHz up to 100kHz. Only one active edge resonant capacitor-assisted soft switching high frequency load resonant cyclo-converter is based on asymmetrical duty cycle PWM strategy. This high frequency cyclo-converter uses bidirectional IGBTs composed of anti-parallel one-chip reverse blocking IGBTs. This high frequency cycloconverter has some remarkable features as electrolytic capacitorless DC busline link, unity power factor correction and sinewave line current shaping, simple configuration with minimum circuit components and low cost, high efficiency and downsizing. This series load resonant cycloconverter incorporating bidirectional active power switches is developed and implemented for high efficiency consumer induction heated food cooking appliances. Its operating principle is described by using equivalent circuits. Its operating performances as soft switching operating ranges and high frequency effective power regulation characteristics are discussed on the basis of simulation and experimental results.
Very High Frequency Resonant DC/DC Converters for LED Lighting
DEFF Research Database (Denmark)
Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.
2013-01-01
This paper presents a very high frequency DC/DC converter for LED lighting. Several resonant topologies are compared and their usability discussed. At the end the resonant SEPIC converter is chosen based on the achievable power density and total bill of material. Simulations of a 51 MHz converter...
Resonance and cut-off surfaces in the ion cyclotron frequency range in toroidal geometry
International Nuclear Information System (INIS)
Resonances and cut-offs of the fast Alfven and ion-cyclotron waves have been studied for a multicomponent plasma in a toroidal axisymmetric geometry. The resonance and cut-off frequencies are given by eigenvalues of ordinary differential equations on the rosonance and cut-off sufaces, respectively. These surfaces coincide with magnetic surfaces. (author)
Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators
Gaskell, J.; Eaves, L.; Novoselov, K. S.; Mishchenko, A.; Geim, A. K.; Fromhold, T. M.; Greenaway, M. T.
2015-01-01
We assess the potential of two-terminal graphene-hBN-graphene resonant tunneling diodes as high-frequency oscillators, using self-consistent quantum transport and electrostatic simulations to determine the time-dependent response of the diodes in a resonant circuit. We quantify how the frequency and power of the current oscillations depend on the diode and circuit parameters including the doping of the graphene electrodes, device geometry, alignment of the graphene lattices, and the circuit i...
Investigation of Frequency-Domain Link Adaptation for a 5-MHz OFDMA/HSDPA system
DEFF Research Database (Denmark)
Pokhariyal, Akhilesh; Kolding, Troels E.; Frederiksen, Frank;
2005-01-01
In this paper, we investigate frequency domain link adaptation (FDLA), e.g. utilizing the frequency selectivity of the channel in an OFDMA system. To make the study specific and based on realistic parameters, we re-use the specifications from a recent 3GPP 5-MHz OFDMA study item. The link...... adaptation and the frequency domain link adaptation are developed in a way compliant with the basic HSDPA specifications. With FDLA we show up to 75% cell throughput gain over the OFDMA reference system at the cost of increased uplink channel quality signaling overhead for frequency selective channels. We...
Sheath-wave-related resonances in the frequency response of a cylindrical monopole in a plasma
International Nuclear Information System (INIS)
A floating or negatively biased antenna immersed in a plasma is surrounded by an ion sheath. The antenna-sheath-plasma system may support slow surface waves at driving frequencies below the electron plasma frequency. Resonances associated with these so-called sheath waves are observed at certain frequencies in the antenna's response to an applied sinusoidal signal. A detailed experimental study of these resonances is presented here for a short cylindrical monopole in a low-pressure isotropic argon plasma. The effect on the resonance frequencies of a dc bias applied to the antenna and of plasma density and antenna length was investigated. Good agreement was obtained with the theoretical predictions derived from a known dispersion equation for sheath waves. From the experimental data, the relationship between sheath thickness and antenna potential, and the frequency dependence of the antenna admittance could be derived
Tao, Ye; Xu, Lijia; Zhang, Zhen; Chen, Runfeng; Li, Huanhuan; Xu, Hui; Zheng, Chao; Huang, Wei
2016-08-01
Current static-state explorations of organic semiconductors for optimal material properties and device performance are hindered by limited insights into the dynamically changed molecular states and charge transport and energy transfer processes upon device operation. Here, we propose a simple yet successful strategy, resonance variation-based dynamic adaptation (RVDA), to realize optimized self-adaptive properties in donor-resonance-acceptor molecules by engineering the resonance variation for dynamic tuning of organic semiconductors. Organic light-emitting diodes hosted by these RVDA materials exhibit remarkably high performance, with external quantum efficiencies up to 21.7% and favorable device stability. Our approach, which supports simultaneous realization of dynamically adapted and selectively enhanced properties via resonance engineering, illustrates a feasible design map for the preparation of smart organic semiconductors capable of dynamic structure and property modulations, promoting the studies of organic electronics from static to dynamic. PMID:27403886
Shoman, Hossam; Dahlem, Marcus S.
2015-02-01
Microring resonators are important elements in a wide variety of optical systems, ranging from optical switches and tunable filterbanks to optical sensors. In these structures, the resonant frequencies are normally controlled by tuning the effective index of refraction. In optical switches and filters, this has traditionally been achieved through electro-optic or thermo-optic effects. In sensors, the effective refractive index is changed by the presence of the measurand. Adding a mechanical degree of freedom to these optical systems allows additional evanescent frequency tuning. In particular, the presence of a cantilever in the near-field of the optical mode can tune the effective refractive index. A specific cantilever displacement can therefore induce a desired resonant frequency shift. Alternatively, a measured shift in the resonant frequency can be associated with a cantilever displacement, and be used for pressure or acceleration sensing. In this paper, we explore a geometry that can be used for controlling the resonant frequency of a microring resonator through evanescent field perturbation, using a cantilever defined in the same silicon layer as the optical waveguides, in a silicon-on-insulator platform. The effects of the lateral gap size between the optical waveguide and the cantilever, and the cantilever vertical displacement, on both the resonant frequency and quality factor of the resonator, are evaluated through finite-difference timedomain computations for wavelengths centered at 1550 nm. The presence of the cantilever in the near-field of the optical mode changes the effective refractive index, resulting in frequency tuning, but also lowers the quality factor due to additional coupling into the membrane.
Point-Wise Phase Matching for Nonlinear Frequency Generation in Dielectric Resonators
Yu, Nan (Inventor); Strekalov, Dmitry V. (Inventor); Lin, Guoping (Inventor)
2016-01-01
An optical resonator fabricated from a uniaxial birefringent crystal, such as beta barium borate. The crystal is cut with the optical axis not perpendicular to a face of the cut crystal. In some cases the optical axis lies in the plane of the cut crystal face. An incident (input) electromagnetic signal (which can range from the infrared through the visible to the ultraviolet) is applied to the resonator. An output signal is recovered which has a frequency that is an integer multiple of the frequency of the input signal. In some cases a prism is used to evanescently couple the input and the output signals to the resonator.
Stochastic resonance in a single-mode laser driven by frequency modulated signal and coloured noises
Institute of Scientific and Technical Information of China (English)
Jin Guo-Xiang; Zhang Liang-Ying; Cao Li
2009-01-01
By adding frequency modulated signals to the intensity equation of gain-noise model of the single-mode laser driven by two coloured noises which are correlated, this paper uses the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity. The results show that the SNR appears typical stochastic resonance with the variation of intensity of the pump noise and quantum noise. As the amplitude of a modulated signal has effects on the SNR, it shows suppression, monotone increasing, stochastic resonance, and multiple stochastic resonance with the variation of the frequency of a carrier signal and modulated signal.
Quantum dot admittance probed at microwave frequencies with an on-chip resonator
Frey, T; Leek, P. J.; M. Beck; Faist, J.; Wallraff, A.; Ensslin, K.; Ihn, T.; Büttiker, M.
2012-01-01
We present microwave frequency measurements of the dynamic admittance of a quantum dot tunnel coupled to a two-dimensional electron gas. The measurements are made via a high-quality 6.75 GHz on-chip resonator capacitively coupled to the dot. The resonator frequency is found to shift both down and up close to conductance resonance of the dot corresponding to a change of sign of the reactance of the system from capacitive to inductive. The observations are consistent with a scattering matrix mo...
Nanotribological surface characterization by frequency modulated torsional resonance mode AFM
Yurtsever, Ayhan
2008-01-01
The aim of this work is to develop an experimental method to measure in-plane surface properties on the nanometer scale by torsional resonance mode atomic force microscopy and to understand the underlying system dynamics. The invention of the atomic force microscope (AFM) and the advances in development of new AFM based techniques have significantly enhanced the capability to probe surface properties with nanometer resolution. However, most of these techniques are based on a flexural oscillat...
Scattering resonance of elastic wave and low-frequency equivalent slow wave
Meng, X.; Liu, H.; Hu, T.; Yang, L.
2015-12-01
Transmitted wave occurs as fast p-wave and slow p-wave in certain conditions when seismic waves travel through inhomogeneous layers. Energy of slow p-waves is strongest at some frequency band, but rather weak at both high frequency band and low frequency band, called scattering resonance. For practical seismic exploration, the frequency of slow p-wave occurs is below 10Hz, which cannot be explained by Biot's theory which predicts existence of the slow p-wave at ultrasonic band in the porous media. The slow p-wave equation have been derived, but which only adapted to explaining slow p-wave in the ultrasonic band. Experimental observations exhibit that slow p-wave also exists in nonporous media but with enormous low-velocity interbeds. When vertical incidence, elastic wave is simplified as compressing wave, the generation of slow waves is independent on shear wave. In the case of flat interbed and gas bubble, Liu (2006) has studied the transmission of acoustic waves, and found that the slow waves below the 10Hz frequency band can be explained. In the case of general elastic anisotropy medium, the tiheoretical research on the generation of slow waves is insufficient. Aiming at this problem, this paper presents an exponential mapping method based on transmitted wave (Magnus 1954), which can successfully explain the generation of the slow wave transmission in that case. Using the prediction operator (Claerbout 1985) to represent the transmission wave, this can be derived as first order partial differential equation. Using expansions in the frequency domain and the wave number domain, we find that the solutions have different expressions in the case of weak scattering and strong scattering. Besides, the method of combining the prediction operator and the exponential map is needed to extend to the elastic wave equation. Using the equation (Frazer and Fryer 1984, 1987), we derive the exponential mapping solution for the prediction operator of the general elastic medium
Lower Bounds on the Frequency Estimation Error in Magnetically Coupled MEMS Resonant Sensors.
Paden, Brad E
2016-02-01
MEMS inductor-capacitor (LC) resonant pressure sensors have revolutionized the treatment of abdominal aortic aneurysms. In contrast to electrostatically driven MEMS resonators, these magnetically coupled devices are wireless so that they can be permanently implanted in the body and can communicate to an external coil via pressure-induced frequency modulation. Motivated by the importance of these sensors in this and other applications, this paper develops relationships among sensor design variables, system noise levels, and overall system performance. Specifically, new models are developed that express the Cramér-Rao lower bound for the variance of resonator frequency estimates in terms of system variables through a system of coupled algebraic equations, which can be used in design and optimization. Further, models are developed for a novel mechanical resonator in addition to the LC-type resonators.
Kim, Dong-Hyun; Chauhan, Munish; Kim, Min-Oh; Jeong, Woo Chul; Kim, Hyung Joong; Sersa, Igor; Kwon, Oh In; Woo, Eung Je
2015-02-01
Electrical conductivities of biological tissues show frequency-dependent behaviors, and these values at different frequencies may provide clinically useful diagnostic information. MR-based tissue property mapping techniques such as magnetic resonance electrical impedance tomography (MREIT) and magnetic resonance electrical property tomography (MREPT) are widely used and provide unique conductivity contrast information over different frequency ranges. Recently, a new method for data acquisition and reconstruction for low- and high-frequency conductivity images from a single MR scan was proposed. In this study, we applied this simultaneous dual-frequency range conductivity mapping MR method to evaluate its utility in a designed phantom and two in vivo animal disease models. Magnetic flux density and B(1)(+) phase map for dual-frequency conductivity images were acquired using a modified spin-echo pulse sequence. Low-frequency conductivity was reconstructed from MREIT data by the projected current density method, while high-frequency conductivity was reconstructed from MREPT data by B(1)(+) mapping. Two different conductivity phantoms comprising varying ion concentrations separated by insulating films with or without holes were used to study the contrast mechanism of the frequency-dependent conductivities related to ion concentration and mobility. Canine brain abscess and ischemia were used as in vivo models to evaluate the capability of the proposed method to identify new electrical properties-based contrast at two different frequencies. The simultaneous dual-frequency range conductivity mapping MR method provides unique contrast information related to the concentration and mobility of ions inside tissues. This method has potential to monitor dynamic changes of the state of disease.
Adaptive synthesis method for broadband array with frequency invariant beam pattern
Institute of Scientific and Technical Information of China (English)
ZHUWeijie; SUNJincai; ZENGXiangyang
2003-01-01
Based on adaptive technique, a design method for broadband array with frequency invariant beam pattern is presented. For a given beam pattern, the all design process can be completed automatically by computer without deriving expression of weight vector. The design process is divided into three steps: (1) Evaluate the weight vector in reference frequency by numerical method. (2) Obtain the weight vectors in other frequency by adaptive technique.(3) For the design target of frequency response given by weight vector at different frequency point, design FIR filter. The proposed method can be applied to arbitrary array and have no restriction on element patterns.
Parametric adaptive time-frequency representation based on time-sheared Gabor atoms
Institute of Scientific and Technical Information of China (English)
Ma Shiwei; Zhu Xiaojin; Chen Guanghua; Wang Jian; Cao Jialin
2007-01-01
A localized parametric time-sheared Gabor atom is derived by convolving a linear frequency modulated factor, modulating in frequency and translating in time to a dilated Gaussian function, which is the generalization of Gabor atom and is more delicate for matching most of the signals encountered in practice, especially for those having frequency dispersion characteristics. The time-frequency distribution of this atom concentrates in its time center and frequency center along energy curve, with the curve being oblique to a certain extent along the time axis. A novel parametric adaptive time-frequency distribution based on a set of the derived atoms is then proposed using a adaptive signal subspace decomposition method in frequency domain, which is non-negative time-frequency energy distribution and free of cross-term interference for multicomponent signals. The results of numerical simulation manifest the effectiveness of the approach in time-frequency representation and signal de-noising processing.
Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators
International Nuclear Information System (INIS)
We assess the potential of two-terminal graphene-hexagonal boron nitride-graphene resonant tunneling diodes as high-frequency oscillators, using self-consistent quantum transport and electrostatic simulations to determine the time-dependent response of the diodes in a resonant circuit. We quantify how the frequency and power of the current oscillations depend on the diode and circuit parameters including the doping of the graphene electrodes, device geometry, alignment of the graphene lattices, and the circuit impedances. Our results indicate that current oscillations with frequencies of up to several hundred GHz should be achievable
Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators
Energy Technology Data Exchange (ETDEWEB)
Gaskell, J.; Fromhold, T. M.; Greenaway, M. T. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Eaves, L. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Novoselov, K. S.; Mishchenko, A. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Geim, A. K. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL (United Kingdom)
2015-09-07
We assess the potential of two-terminal graphene-hexagonal boron nitride-graphene resonant tunneling diodes as high-frequency oscillators, using self-consistent quantum transport and electrostatic simulations to determine the time-dependent response of the diodes in a resonant circuit. We quantify how the frequency and power of the current oscillations depend on the diode and circuit parameters including the doping of the graphene electrodes, device geometry, alignment of the graphene lattices, and the circuit impedances. Our results indicate that current oscillations with frequencies of up to several hundred GHz should be achievable.
Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators
Gaskell, J.; Eaves, L.; Novoselov, K. S.; Mishchenko, A.; Geim, A. K.; Fromhold, T. M.; Greenaway, M. T.
2015-09-01
We assess the potential of two-terminal graphene-hexagonal boron nitride-graphene resonant tunneling diodes as high-frequency oscillators, using self-consistent quantum transport and electrostatic simulations to determine the time-dependent response of the diodes in a resonant circuit. We quantify how the frequency and power of the current oscillations depend on the diode and circuit parameters including the doping of the graphene electrodes, device geometry, alignment of the graphene lattices, and the circuit impedances. Our results indicate that current oscillations with frequencies of up to several hundred GHz should be achievable.
Sok, J; Lee, E H
1998-01-01
An applied dc voltage varies the dielectric constant of ferroelectric SrTiO sub 3 films. A tuning mechanism for superconducting microwave resonators was realized by using the variation in the dielectric constant of SrTiO sub 3 films. In order to estimate the values of the capacitance, C, and the loss tangent, tan delta, of SrTiO sub 3 ferroelectric capacitors, we used high-temperature superconducting microwave resonators which were composed of two ports, two poles, and dc bias circuits at the zero-field points. SrTiO sub 3 ferroelectric capacitors successfully controlled the resonant frequency of the resonator. Resonant frequencies of 3.98 GHz and 4.20 GHz were measured at bias voltages of 0 V and 50 V which correspond to capacitance values of 0.94 pF and 0.7pF, respectively. The values of the loss tangent, tan delta sub e sub f sub f , obtained in this measurements, were about 0.01.
Richert, Ranko
2007-05-01
The impedance of a capacitor which embraces a charged cantilever is used to measure the mechanical properties of the cantilever material. The technique has been tested with an amorphous metallic specimen, but is applicable for many other solids. The material damping can be measured at the resonance frequency of the cantilever via the width of the resonance curve or by recording the ring-down behavior. Additionally, several decades in frequency are accessible below the resonance frequency, where values as low as nu=0.03 Hz are achieved easily. The data are analyzed with a single equation that captures the damping at all frequencies in terms of the material specific Young's modulus E and its loss angle tan delta=E"/E'.
Off-resonance frequency operation for power transfer in a loosely coupled air core transformer
Scudiere, Matthew B
2012-11-13
A power transmission system includes a loosely coupled air core transformer having a resonance frequency determined by a product of inductance and capacitance of a primary circuit including a primary coil. A secondary circuit is configured to have a substantially same product of inductance and capacitance. A back EMF generating device (e.g., a battery), which generates a back EMF with power transfer, is attached to the secondary circuit. Once the load power of the back EMF generating device exceeds a certain threshold level, which depends on the system parameters, the power transfer can be achieved at higher transfer efficiency if performed at an operating frequency less than the resonance frequency, which can be from 50% to 95% of the resonance frequency.
Unprecedented High Long Term Frequency Stability with a Macroscopic Resonator Oscillator
Grop, Serge; Bourgeois, Pierre-Yves; Bazin, Nicolas; Kersalé, Yann; Oxborrow, Mark; Rubiola, Enrico; Giordano, Vincent
2010-01-01
This article reports on the long-term frequency stabilty characterisation of a new type of cryogenic sapphire oscillator using an autonomous pulse-tube cryocooler as its cold source. This new design enables a relative frequency stability of better than 4.5e-15 over one day of integration. This represents to our knowledge the best long-term frequency stability ever obtained with a signal source based on a macroscopic resonator.
Resonant and nonresonant magnetoelectric effects in multilayer composites at microwave frequencies
Petrov, V. M.; Bichurin, M. I.; Kiliba, Yu. V.; Srinivasan, G.
2002-03-01
A phenomenological theory is presented on the effect of an external electric field on magnetic and magnetoelectric (ME) susceptibilities of ferroelectric/ferromagnetic composites, such as lithium ferrite lead zirconate titanate (PZT), at microwave frequencies. Expressions have been obtained relating the magnetic susceptibility tensor components of the composite (symmetry point group 3m and 4mm) to ME coupling constants. Estimates of linear and bilinear ME susceptibilities at high frequencies are given and are extended to include ferromagnetic resonance (FMR) conditions [1]. Both magnetic and ME susceptibilities reveal a resonance in the electric field dependence. Three methods for measurements of ME susceptibility at microwave frequencies are considered: electric dipole transitions, resonance ME effects at ferromagnetic resonance and off-resonance method. Using the theory and experimental data on ferromagnetic resonance line shift in external electric field, the ME constants for lithium ferrite-PZT multilayer composite are determined. The theory is useful for measurements of ME constants and for the design and analysis of electrically controlled high frequency magnetic devices. - work supported by a grant from the National Science Foundation (DMR-0072144) 1. M.I. Bichurin, I. A. Kornev, V. M. Petrov, A. S. Tatarenko, Yu. V. Kiliba, and G. Srinivasan, Phys. Rev. B 64, 094409 (2001).
Spike-frequency adaptation generates intensity invariance in a primary auditory interneuron.
Benda, Jan; Hennig, R Matthias
2008-04-01
Adaptation of the spike-frequency response to constant stimulation, as observed on various timescales in many neurons, reflects high-pass filter properties of a neuron's transfer function. Adaptation in general, however, is not sufficient to make a neuron's response independent of the mean intensity of a sensory stimulus, since low frequency components of the stimulus are still transmitted, although with reduced gain. We here show, based on an analytically tractable model, that the response of a neuron is intensity invariant, if the fully adapted steady-state spike-frequency response to constant stimuli is independent of stimulus intensity. Electrophysiological recordings from the AN1, a primary auditory interneuron of crickets, show that for intensities above 60 dB SPL (sound pressure level) the AN1 adapted with a time-constant of approximately 40 ms to a steady-state firing rate of approximately 100 Hz. Using identical random amplitude-modulation stimuli we verified that the AN1's spike-frequency response is indeed invariant to the stimulus' mean intensity above 60 dB SPL. The transfer function of the AN1 is a band pass, resulting from a high-pass filter (cutoff frequency at 4 Hz) due to adaptation and a low-pass filter (100 Hz) determined by the steady-state spike frequency. Thus, fast spike-frequency adaptation can generate intensity invariance already at the first level of neural processing.
Frequency shifts of resonant modes of the Sun due to near-surface convective scattering
Bhattacharya, Jishnu; Antia, H M
2015-01-01
Measurements of oscillation frequencies of the Sun and stars can provide important independent constraints on their internal structure and dynamics. Seismic models of these oscillations are used to connect structure and rotation of the star to its resonant frequencies, which are then compared with observations, the goal being that of minimizing the difference between the two. Even in the case of the Sun, for which structure models are highly tuned, observed frequencies show systematic deviations from modeled frequencies, a phenomenon referred to as the "surface term." The dominant source of this systematic effect is thought to be vigorous near-surface convection, which is not well accounted for in both stellar modeling and mode-oscillation physics. Here we bring to bear the method of homogenization, applicable in the asymptotic limit of large wavelengths (in comparison to the correlation scale of convection), to characterize the effect of small-scale surface convection on resonant-mode frequencies in the Sun....
Frequency Stability of Atomic Clocks Based on Coherent Population Trapping Resonance in 85Rb
Institute of Scientific and Technical Information of China (English)
LIU Lu; GUO Tao; DENG Ke; LIU Xin-Yuan; CHEN Xu-Zong; WANG Zhong
2007-01-01
An atomic clock system based on coherent population trapping (CPT) resonance in 85Rb is reported, while most past works about the CPT clock are in 87Rb. A new modulation method (full-hyperfine-frequency-splitting modulation) is presented to reduce the effect of light shift to improve the frequency stability of the CPT clock in 85Rb. The experimental results show that the short-term frequency stability of the CPT clock in 85Rb is in the order of 10-10/s and the long-term frequency stability can achieve 1.5 × 10-11 /80000s, which performs as well as 87Rb in CPT resonance. This very good frequency stability performance associated with the low-cost and low-power properties of 85Rb indicates that an atomic clock based on CPT in 85 Rb should be a promising candidate for making the chip scale atomic clock.
Energy Technology Data Exchange (ETDEWEB)
Sun, Kyung Ho; Kim, Young-Cheol [Department of System Dynamics, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yuseong-Gu, Daejeon 305-343 (Korea, Republic of); Kim, Jae Eun, E-mail: jekim@cu.ac.kr [School of Mechanical and Automotive Engineering, Catholic University of Daegu, 13-13 Hayang-Ro, Hayang-Eup, Gyeongsan-Si, Gyeongsangbuk-Do 712-702 (Korea, Republic of)
2014-10-15
While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm{sup 3}, which was designed for a target frequency of as low as 100 Hz.
Energy Technology Data Exchange (ETDEWEB)
Hu, M.; Bai, Y. Z., E-mail: abai@mail.hust.edu.cn; Zhou, Z. B., E-mail: zhouzb@mail.hust.edu.cn; Li, Z. X.; Luo, J. [MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)
2014-05-15
The capacitive transducer with differential transformer bridge is widely used in ultra-sensitive space accelerometers due to their simple structure and high resolution. In this paper, the front-end electronics of an inductive-capacitive resonant bridge transducer is analyzed. The analysis result shows that the performance of this transducer depends upon the case that the AC pumping frequency operates at the resonance point of the inductive-capacitive bridge. The effect of possible mismatch between the AC pumping frequency and the actual resonant frequency is discussed, and the theoretical analysis indicates that the output voltage noise of the front-end electronics will deteriorate by a factor of about 3 due to either a 5% variation of the AC pumping frequency or a 10% variation of the tuning capacitance. A pre-scanning method to determine the actual resonant frequency is proposed followed by the adjustment of the operating frequency or the change of the tuning capacitance in order to maintain expected high resolution level. An experiment to verify the mismatching effect and the adjustment method is provided.
Hu, M.; Bai, Y. Z.; Zhou, Z. B.; Li, Z. X.; Luo, J.
2014-05-01
The capacitive transducer with differential transformer bridge is widely used in ultra-sensitive space accelerometers due to their simple structure and high resolution. In this paper, the front-end electronics of an inductive-capacitive resonant bridge transducer is analyzed. The analysis result shows that the performance of this transducer depends upon the case that the AC pumping frequency operates at the resonance point of the inductive-capacitive bridge. The effect of possible mismatch between the AC pumping frequency and the actual resonant frequency is discussed, and the theoretical analysis indicates that the output voltage noise of the front-end electronics will deteriorate by a factor of about 3 due to either a 5% variation of the AC pumping frequency or a 10% variation of the tuning capacitance. A pre-scanning method to determine the actual resonant frequency is proposed followed by the adjustment of the operating frequency or the change of the tuning capacitance in order to maintain expected high resolution level. An experiment to verify the mismatching effect and the adjustment method is provided.
Directory of Open Access Journals (Sweden)
Kyung Ho Sun
2014-10-01
Full Text Available While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm3, which was designed for a target frequency of as low as 100 Hz.
Cantrell, Sean A.; Cantrell, John H.; Lillehei, Peter T.
2007-01-01
A scanning probe microscope methodology, called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), has been developed. The method employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope engages the sample top surface. The cantilever is driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave at the sample surface generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create amplitude and phase-generated images of nanoscale near-surface and subsurface features. RDF-AFUM phase images of LaRC-CP2 polyimide polymer containing embedded nanostructures are presented. A RDF-AFUM micrograph of a 12.7 micrometer thick film of LaRC-CP2 containing a monolayer of gold nanoparticles embedded 7 micrometers below the specimen surface reveals the occurrence of contiguous amorphous and crystalline phases within the bulk of the polymer and a preferential growth of the crystalline phase in the vicinity of the gold nanoparticles. A RDF-AFUM micrograph of LaRC-CP2 film containing randomly dispersed carbon nanotubes reveals the growth of an interphase region at certain nanotube-polymer interfaces.
Selective engineering of cavity resonance for frequency matching in optical parametric processes
Energy Technology Data Exchange (ETDEWEB)
Lu, Xiyuan; Rogers, Steven [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Jiang, Wei C. [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States); Lin, Qiang, E-mail: qiang.lin@rochester.edu [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States); Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627 (United States)
2014-10-13
We propose to selectively engineer a single cavity resonance to achieve frequency matching for optical parametric processes in high-Q microresonators. For this purpose, we demonstrate an approach, selective mode splitting (SMS), to precisely shift a targeted cavity resonance, while leaving other cavity modes intact. We apply SMS to achieve efficient parametric generation via four-wave mixing in high-Q silicon microresonators. The proposed approach is of great potential for broad applications in integrated nonlinear photonics.
DEVELOPMENT OF ACOUSTIC MODELS FOR HIGH FREQUENCY RESONATORS FOR TURBOCHARGED IC-ENGINES
Wang, Zheng
2012-01-01
Automotive turbo compressors generate high frequency noise in the air intake system. This sound generation is of importance for the perceived sound quality of luxury cars and may need to be controlled by the use of silencers. The silencers usually contain resonators with slits, perforates and cavities. The purpose of the work reported is to develop acoustic models for these resonators where relevant effects such as the effect of realistic mean flow on losses and possibly 3D effects are consid...
Selective engineering of cavity resonance for frequency matching in optical parametric processes
Lu, Xiyuan; Jiang, Wei C; Lin, Qiang
2014-01-01
We propose to selectively engineer a single cavity resonance to achieve frequency matching for optical parametric processes in high-Q microresonators. For this purpose, we demonstrate an approach, selective mode splitting (SMS), to precisely shift a targeted cavity resonance, while leaving other cavity modes intact. We apply SMS to achieve efficient parametric generation via four-wave mixing in high-Q silicon microresonators. The proposed approach is of great potential for broad applications in integrated nonlinear photonics.
Sborikas, Martynas; Wegener, Michael
2013-12-01
Ferroelectrets are piezoelectric materials suitable for acoustic applications such as airborne ultrasonic transducers. Typical ferroelectrets exhibit resonance frequencies in the high kHz to low MHz range. In order to decrease the transducer resonance frequencies to the low kHz range, processes such as gas-diffusion expansion and electric charging were adjusted to cellular films which are initially twice as thick as in earlier studies. The demonstrated film expansion and electric charging lead to mechanically soft cellular structures which show high piezoelectric activities with coefficients up to 130 pC/N. Due to the simultaneously increased film thicknesses, the resonance frequencies are lowered down to about 233 kHz.
Energy Technology Data Exchange (ETDEWEB)
Kudo, Kiwamu, E-mail: kiwamu.kudo@toshiba.co.jp; Suto, Hirofumi; Nagasawa, Tazumi; Mizushima, Koichi; Sato, Rie [Corporate Research and Development Center, Toshiba Corporation, Kawasaki 212–8582 (Japan)
2014-10-28
The fundamental function of any oscillator is to produce a waveform with a stable frequency. Here, we show a method of frequency stabilization for spin-torque nano-oscillators (STNOs) that relies on coupling with an adjacent nanomagnet through the magnetic dipole–dipole interaction. It is numerically demonstrated that highly stable oscillations occur as a result of mutual feedback between an STNO and a nanomagnet. The nanomagnet acts as a nonlinear resonator for the STNO. This method is based on the nonlinear behavior of the resonator and can be considered as a magnetic analogue of an optimization scheme in nanoelectromechanical systems. The oscillation frequency is most stabilized when the nanomagnet is driven at a special feedback point at which the feedback noise between the STNO and resonator is completely eliminated.
Magnetic Earth Ionosphere Resonant Frequencies (NASA-MEIRF Project)
1994-01-01
During this current reporting period, the project has focused on completing Phase 1 of the field monitoring work and documenting research results. Highlights of these efforts include presentations of papers at the annual joint meeting of the American Physical Society/American Association of Physics Teachers, April 18-22, 1994, in Crystal City, Virginia, and at the International Space, Time, and Gravitation Conference and Etoiles de L'Ecole Polytechnique Symposium, May 23-28, 1994, in St. Petersburg, Russia. Field measurements of the background ultra low frequency (ULF) electromagnetic spectrum in the New Mexico and Texas regions show interesting differences. Included are papers entitled 'Triplet Solution of the Twin Paradox' and 'Classical Electron Mass and Fields, Part 3.'
Farnesi, D.; Chiavaioli, F.; Baldini, F.; Cosi, F.; Righini, G. C.; Soria, S.; Trono, C.; Nunzi Conti, G.
2016-03-01
A novel optical fiber coupler to whispering gallery mode (WGM) micro-resonators, which allows frequency selective addressing of different micro-resonators along the same fiber, is proposed. The coupling unit is based on a pair of identical long period fiber gratings (LPGs) and a thick adiabatic taper (>15 μm in waist) in between, where evanescent coupling from cladding modes to WGMs takes place. This robust unit can be replicated more times along the same fiber, simply cascading LPGs with different bands. Independent addressing of two different resonators along the same fiber is demonstrated.
Arnold tongues for a resonant injection-locked frequency divider: analytical and numerical results
Bartuccelli, Michele V; Gentile, Guido; Schilder, Frank
2009-01-01
In this paper we consider a resonant injection-locked frequency divider which is of interest in electronics, and we investigate the frequency locking phenomenon when varying the amplitude and frequency of the injected signal. We study both analytically and numerically the structure of the Arnold tongues in the frequency-amplitude plane. In particular, we provide exact analytical formulae for the widths of the tongues, which correspond to the plateaux of the devil's staircase picture. The results account for numerical and experimental findings presented in the literature for special driving terms and, additionally, extend the analysis to a more general setting.
Lee, Manhee; Hwang, Jong Geun; Jahng, Junghoon; Kim, QHwan; Noh, Hanaul; An, Sangmin; Jhe, Wonho
2016-08-01
We present an electrical feedback method for independent and simultaneous tuning of both the resonance frequency and the quality factor of a harmonic oscillator, the so called "qPlus" configuration of quartz tuning forks. We incorporate a feedback circuit with two electronic gain parameters into the original actuation-detection system, and systematically demonstrate the control of the original resonance frequency of 32 592 Hz from 32 572 Hz to 32 610 Hz and the original quality factor 952 from 408 up to 20 000. This tunable module can be used for enhancing and optimizing the oscillator performance in compliance with specifics of applications.
Resonance of Gaussian Electromagnetic Field to the High Frequency Gravitational Waves
Li, Jin; Zhang, Lu; Lin, Kai; Wen, Hao
2016-08-01
We consider a Gaussian Beam (GB) resonant system for high frequency gravitational waves (HFGWs) detection. At present, we find the optimal signal strength in theory through setting the magnetic component of GB in a standard gaussian form. Under the synchro-resonance condition, we study the signal strength (i.e., transverse perturbative photon fluxes) from the relic HFGWs (predicted by ordinary inflationary model) and the braneworld HFGWs (from braneworld scenarios). Both of them would generate potentially detectable transverse perturbative photon fluxes (PPFs). Furthermore we find optimal system parameters and the relationship between frequency and effective width of energy fluxes accumulation.
Analytical Model of Fixed-Frequency Variable Duty-Cycle Controlled LLC Resonant Converter
DEFF Research Database (Denmark)
Shen, Yanfeng; Wang, Huai; Blaabjerg, Frede;
2016-01-01
For LLC resonant converters, the fixed-frequency variable duty-cycle control is usually combined with the variable frequency (VF) control to widen the gain range, improve light-load efficiency or suppress the inrush current during start-up. However, both the operation mode and the steady...... is derived, which makes the fast and automatic design optimization possible. The critical characteristics, such as dc voltage gain, peak resonant current, peak capacitor voltage, rms current as well as the constraint conditions for the operation mode are developed and verified with simulation...
Wang, Wanjun; Zhou, Jie; Wang, Jun; Feng, Junbo; Guo, Jin
2015-10-01
In this paper, a compact silicon photonics circuit is proposed. It consists of add-drop filter, input/output grating coupler. The resonance peak of add-drop filter can be tuned with the assist of p-i-n diode. The unknown frequency of microwave is loaded at the optical wave and coupled into the chip. The optical power ratio of through port and drop port is monotonous, which is corresponding to the unknown frequency. Meanwhile, the resonance peak of the ring can shift with the assist of p-i-n diode.
Exact thickness-shear resonance frequency of electroded piezoelectric crystal plates
Institute of Scientific and Technical Information of China (English)
WANG Ji; SHEN Li-jun
2005-01-01
The determination of the precise thickness-shear frequency of electroded crystal plates has practical importance in quartz crystal resonator design and fabrication, especially when the high fundamental thickness-shear frequency has reduced the crystal plate thickness to such a degree that proper consideration of the effect of electrodes is very important. The electrodes effect as mass loading in the estimation of the resonance frequency has to be modified to consider the stiffness of electrodes, as the relative strength is increasingly noticeable. By following a known procedure in the determination of the thickness-shear frequency of an infinite AT-cut crystal plate, frequency equations of crystal plate without and with piezoelectric effect are obtained in terms of elastic constants and the electrode material density. After solving these equations for the usual design parameters of crystal resonators, the design process can be optimized to pinpoint the precise configuration to avoid time-consuming trial and reduction steps. Since these equations and solutions are presented for widely used materials and parameters, they can be easily integrated into the existing crystal resonator design and manufacturing processes.
Cho, Franklin H; Takahashi, Susumu
2014-01-01
We describe instrumentation for a high-frequency electron paramagnetic resonance (EPR) and pulsed electron-electron double resonance (PELDOR) spectroscopy. The instrumentation is operated in the frequency range of 107$-$120 GHz and 215$-$240 GHz and in the magnetic field range of 0$-$12.1 Tesla. The spectrometer consisting of a high-frequency high-power solid-state source, a quasioptical system, a phase-sensitive detection system, a cryogenic-free superconducting magnet and a $^4$He cryostat enables multi-frequency continuous-wave EPR spectroscopy as well as pulsed EPR measurements with a few hundred nanosecond pulses. Here we discuss the details of the design and the pulsed EPR sensitivity of the instrumentation. We also present performance of the instrumentation in unique experiments including PELDOR spectroscopy to probe correlations in an insulating electronic spin system and application of dynamical decoupling techniques to extend spin coherence of electron spins in an insulating solid-state system.
High-frequency QPOs as a problem in physics: non-linear resonance
Kluzniak, W; Lee, W H; Abramowicz, Marek A.; Kluzniak, Wlodek; Lee, William H.
2004-01-01
The presence of a kHz frequency in LMXBs has been expected from scaling laws, by analogy with the QPO phenomenon in HMXB X-ray pulsars. Interpretation of the two kHz frequencies, observed in accreting neutron stars, in terms of non-linear resonance in strong-field gravity led to the prediction of twin QPOs in black hole systems, in a definite frequency ratio (such as 2/3). The imprint of a subharmonic of the 401 Hz rotation rate in the frequencies of the QPOs detected in the accreting millisecond pulsar is at once a signature of non-linear resonance and of coupling between accretion disk modes and the neutron star spin.
Microwave and RF Applications for Micro-resonator based Frequency Combs
Nguyen, Thach G; Ferrera, Marcello; Pasquazi, Alessia; Peccianti, Marco; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J
2015-01-01
Photonic integrated circuits that exploit nonlinear optics in order to generate and process signals all-optically have achieved performance far superior to that possible electronically - particularly with respect to speed. We review the recent achievements based in new CMOS-compatible platforms that are better suited than SOI for nonlinear optics, focusing on radio frequency (RF) and microwave based applications that exploit micro-resonator based frequency combs. We highlight their potential as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We review recent work on a photonic RF Hilbert transformer for broadband microwave in-phase and quadrature-phase generation based on an integrated frequency optical comb. The comb is generated using a nonlinear microring resonator based on a CMOS compatible, high-index contr...
Adaptive control of linear multivariable systems with high frequency gain matrix hurwitz
Institute of Scientific and Technical Information of China (English)
Ying ZHOU; Yuqiang WU; Shumin FEI
2005-01-01
A new adaptive control scheme is proposed for multivariable model reference adaptive control(MRAC) systems based on the nonlinear backstepping approach with vector form.The assumption on a priori knowledge of the high frequency gain matrix in existing results is relaxed and the new required condition for the high frequency gain matrix can be easily checked for certain plants so that the proposed method is widely applicable.This control scheme guarantees the global stability of the closed-loop systems and the tracking error can be arbitrary small.The simulation result for an application example shows the validity of the proposed nonlinear adaptive scheme.
Optical frequency comb generation from aluminum nitride micro-ring resonator
Jung, Hojoong; Xiong, Chi; Fong, King Y.; Zhang, Xufeng; Hong X. Tang
2013-01-01
Aluminum nitride is an appealing nonlinear optical material for on-chip wavelength conversion. Here we report optical frequency comb generation from high quality factor aluminum nitride micro-ring resonators integrated on silicon substrates. By engineering the waveguide structure to achieve near-zero dispersion at telecommunication wavelengths and optimizing the phase matching for four-wave mixing, frequency combs are generated with a single wavelength continuous-wave pump laser. The Kerr coe...
High Frequency Soft Switching Of PWM Boost Converter Using Auxiliary Resonant Circuit
C. P. Sai Kiran; M. Vishnu Vardhan
2014-01-01
This thesis presents High frequency Soft Switching DC-DC boost Converter. The circuit consists of a general Boost Converter with an additional resonant circuit which has a switch, inductor, capacitor and a diode.In general Boost Converter circuits have snubber circuits where switching losses are dissipated in external passive resistors; which is known as hard switching. As the switching frequency of PWM converters is increased its switching losses and conduction losses also in...
Resonance frequency shift in a cavity with a thin conducting film near a conducting wall
Energy Technology Data Exchange (ETDEWEB)
Braggio, C. [Dipartimento di Fisica, Universita di Ferrara and INFN, Via del Paradiso 12, 44100 Ferrara (Italy)]. E-mail: caterina.braggio@lnl.infn.it; Bressi, G. [INFN, Sezione di Pavia, Via Bassi 6, 27100 Pavia (Italy); Carugno, G. [INFN, Sezione di Padova, Via F. Marzolo 8, 35131 Padova (Italy); Dodonov, A.V. [Departamento de Fisica, Universidade Federal de Sao Carlos, Via Washington Luiz, Km 235, Sao Carlos 13565-905, SP (Brazil); Dodonov, V.V. [Instituto de Fisica, Universidade de Brasilia, Caixa Postal 04455, 70910-900 Brasilia, DF (Brazil)]. E-mail: vdodonov@fis.unb.br; Galeazzi, G. [INFN, LNL, Viale dell' Universita 2, 35020 Legnaro (Italy); Ruoso, G. [INFN, LNL, Viale dell' Universita 2, 35020 Legnaro (Italy); Zanello, D. [INFN, Sezione di Roma, Piazzale A. Moro 2, 00185 Roma (Italy)
2007-03-19
We show that a very thin conducting film (whose thickness can be much smaller than the skin depth), placed nearby a wall of an electromagnetic cavity, can produce the same shift of the resonance frequency as a bulk conducting slab, provided the displacement of the film from the wall is much bigger than the skin depth. We derive a simple analytical formula for the frequency shift and compare it with exact numerical calculations and experimental data.
Compensation of temperature frequency pushing in microwave resonator-meters on the basis VCO
Directory of Open Access Journals (Sweden)
Drobakhin O. O.
2008-02-01
Full Text Available It is shown that the influence of temperature oscillations on the error of measurements of parameters in the case of the application of microwave resonator meters on the basis of a voltage-controlled oscillator (VCO can be minimized by software using a special algorithm of VCO frequency setting correction. An algorithm of VCO frequency setting correction for triangle control voltage is proposed.
Low power very high frequency resonant converter with high step down ratio
DEFF Research Database (Denmark)
Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.
2013-01-01
This paper presents the design of a resonant converter with a switching frequency in the very high frequency range (30-300MHz), a large step down ratio and low output power. This gives the designed converters specifications which are far from previous results. The class E inverter and rectifier...... is with a large input inductor. The power stages are designed with the same specs and efficiencies from 60.7−82.9% are achieved....
Frequency Dependence of Resonance Field of One-Dimensional Heisenberg Antiferromagnet KCuF3
Institute of Scientific and Technical Information of China (English)
SHI Qing-Fan; L(U) Zhen; MA Mu-Yan; MA Chao; LI Liang-Sheng
2006-01-01
@@ The frequency dependence of the in-plane angular change of the antiferromagnetic resonance (AFMR) field of KCuF3 is systematically measured at frequencies ranging from 3.8 to 10.6 GHz at 4.2K. The effect of inequivalent g-tensors is found to gradually diminish with decreasing the frequency, and completely vanish when the frequency is decreased to the lower-frequency branch of C-band, while the effect of the effective anisotropy field is significantly enhanced with decreasing the frequency. The calculated AFMR field Hres based on the eight-sublattice model proposed by Yamada and Kato [J. Phys. Soc. Jpn. 63 (1994)289] is in good agreement with the experimental data.
Shakhmuratov, R N
2016-01-01
The resonant filtering method transforming frequency modulated radiation field into a train of short pulses is proposed to apply in optical domain. Effective frequency modulation can be achieved by electro-optic modulator or by resonant frequency modulation of the filter with a narrow absorption line. Due to frequency modulation narrow-spectrum CW radiation field is seen by the resonant filter as a comb of equidistant spectral components separated by the modulation frequency. Tuning narrow-bandwidth filter in resonance with $n$-th spectral component of the comb transforms the radiation field into bunches of pulses with $n$ pulses in each bunch. The transformation is explained by the interference of the coherently scattered resonant component of the field with the whole comb. Constructive interference results in formation of pulses, while destructive interference is seen as dark windows between pulses. It is found that the optimal thickness of the resonant filter is several orders of magnitude smaller than the...
DEFF Research Database (Denmark)
De Poorter, J; De Wagter, C; De Deene, Y;
1995-01-01
The noninvasive thermometry method is based on the temperature dependence of the proton resonance frequency (PRF). High-quality temperature images can be obtained from phase information of standard gradient-echo sequences with an accuracy of 0.2 degrees C in phantoms. This work was focused...
Berg, Anne T.; Mathern, Gary W.; Bronen, Richard A.; Fulbright, Robert K.; DiMario, Francis; Testa, Francine M.; Levy, Susan R.
2009-01-01
The epidemiology of lesions identified by magnetic resonance imaging (MRI), along with the use of pre-surgical evaluations and surgery in childhood-onset epilepsy patients has not previously been described. In a prospectively identified community-based cohort of children enrolled from 1993 to 1997, we examined (i) the frequency of lesions…
Optical fiber strain sensor using fiber resonator based on frequency comb Vernier spectroscopy
DEFF Research Database (Denmark)
Zhang, Liang; Lu, Ping; Chen, Li;
2012-01-01
A novel (to our best knowledge) optical fiber strain sensor using a fiber ring resonator based on frequency comb Vernier spectroscopy is proposed and demonstrated. A passively mode-locked optical fiber laser is employed to generate a phased-locked frequency comb. Strain applied to the optical fiber...... of the fiber ring resonator can be measured with the transmission spectrum. A good linearity is obtained between displacement and the inverse of wavelength spacing with an R2 of 0.9989, and high sensitivities better than 40 pm/με within the range of 0 to 10 με are achieved. The sensitivity can...... be proportionally improved by increasing the length of the optical fiber ring resonator....
Yin, Hanjun; Zhao, Jianguo; Tang, Genyang; Ma, Xiaoyi; Wang, Shangxu
2016-06-01
Differential acoustic resonance spectroscopy (DARS) has been developed to determine the elastic properties of saturated rocks within the kHz frequency range. This laboratory technique is based on considerations from perturbation theory, wherein the resonance frequencies of the resonant cavity with and without a perturbation sample are used to estimate the acoustic properties of the test sample. In order to better understand the operating mechanism of DARS and therefore optimize the procedure, it is important to develop an accurate and efficient numerical model. Accordingly, this study presents a new multiphysics model by coupling together considerations from acoustics, solid mechanics, and electrostatics. The numerical results reveal that the newly developed model can successfully simulate the acoustic pressure field at different resonance modes, and that it can accurately reflect the measurement process. Based on the understanding of the DARS system afforded by the numerical simulation, we refine the system configuration by utilizing cavities of different lengths and appropriate radii to broaden the frequency bandwidth and ensure testing accuracy. Four synthetic samples are measured to test the performance of the optimized DARS system, in conjunction with ultrasonic and static measurements. For nonporous samples, the estimated bulk moduli are shown to be independent of the different measurement methods (i.e. DARS or ultrasonic techniques). In contrast, for sealed porous samples, the differences in bulk moduli between the low- and high-frequency techniques can be clearly observed; this discrepancy is attributed to frequency dispersion. In summary, the optimized DARS system with an extended frequency range of 500-2000 Hz demonstrates considerable utility in investigating the frequency dependence of the acoustic properties of reservoir rocks.
Adaptive Feed-Forward Control of Low Frequency Interior Noise
Kletschkowski, Thomas
2012-01-01
This book presents a mechatronic approach to Active Noise Control (ANC). It describes the required elements of system theory, engineering acoustics, electroacoustics and adaptive signal processing in a comprehensive, consistent and systematic manner using a unified notation. Furthermore, it includes a design methodology for ANC-systems, explains its application and describes tools to be used for ANC-system design. From the research point of view, the book presents new approaches to sound source localization in weakly damped interiors. One is based on the inverse finite element method, the other is based on a sound intensity probe with an active free field. Furthermore, a prototype of an ANC-system able to reach the physical limits of local (feed-forward) ANC is described. This is one example for applied research in ANC-system design. Other examples are given for (i) local ANC in a semi-enclosed subspace of an aircraft cargo hold and (ii) for the combination of audio entertainment with ANC.
Spectral and angular characteristics of dielectric resonator metasurface at optical frequencies
Energy Technology Data Exchange (ETDEWEB)
Zou, Longfang [School of Electrical and Electronic Engineering, The University of Adelaide, Adelaide, SA 5005 (Australia); Department of Electrical and Electronic Engineering, The University of Bristol, Bristol, BS8 1TH (United Kingdom); López-García, Martin; Oulton, Ruth; Klemm, Maciej [Department of Electrical and Electronic Engineering, The University of Bristol, Bristol, BS8 1TH (United Kingdom); Withayachumnankul, Withawat; Fumeaux, Christophe, E-mail: christophe.fumeaux@adelaide.edu.au [School of Electrical and Electronic Engineering, The University of Adelaide, Adelaide, SA 5005 (Australia); Shah, Charan M.; Mitchell, Arnan; Bhaskaran, Madhu; Sriram, Sharath [Functional Materials and Microsystems Research Group, School of Electrical and Computer Engineering, RMIT University, Melbourne VIC 3001 (Australia)
2014-11-10
The capability of manipulating light at subwavelength scale has fostered the applications of flat metasurfaces in various fields. Compared to metallic structure, metasurfaces made of high permittivity low-loss dielectric resonators hold the promise of high efficiency by avoiding high conductive losses of metals at optical frequencies. This letter investigates the spectral and angular characteristics of a dielectric resonator metasurface composed of periodic sub-arrays of resonators with a linearly varying phase response. The far-field response of the metasurface can be decomposed into the response of a single grating element (sub-array) and the grating arrangement response. The analysis also reveals that coupling between resonators has a non-negligible impact on the angular response. Over a wide wavelength range, the simulated and measured angular characteristics of the metasurface provide a definite illustration of how different grating diffraction orders can be selectively suppressed or enhanced through antenna sub-array design.
Arnol'd tongues for a resonant injection-locked frequency divider: analytical and numerical results
DEFF Research Database (Denmark)
Bartuccelli, Michele; Deane, Jonathan H.B.; Gentile, Guido;
2010-01-01
In this paper we consider a resonant injection-locked frequency divider which is of interest in electronics, and we investigate the frequency locking phenomenon when varying the amplitude and frequency of the injected signal. We study both analytically and numerically the structure of the Arnol......’d tongues in the frequency–amplitude plane. In particular, we provide exact analytical formulae for the widths of the tongues, which correspond to the plateaux of the devil’s staircase picture. The results account for numerical and experimental findings presented in the literature for special driving terms...... and, additionally, extend the analysis to a more general setting....
A Experimental Determination of the Resonant Frequency of Atoms Moving in a Medium
Beary, Daniel Andrew
The theory of the Doppler-Recoil effect is described. In contrast to previous theories, the theory proposed by Haugan and Kowalski suggests that the frequency of the electromagnetic wave that excites a transition in an atom is a function of the velocity of that atom and the index of refraction of the medium. Following the path of Haugan and Kowalski, the Doppler Recoil equation is derived under the conditions of a rarefied gas acting as a continuous medium. Next, the theory of saturation spectroscopy is revised. This method of spectroscopy uses a pump and probe beam traveling collinearly in opposite directions. Beams of equal frequency in the lab frame interact with the zero axial velocity population within the gas when the beams are on resonance. For pump and probe beams of different frequencies, the atoms that they interact with will have an axial velocity component such that the Doppler shift leads to resonance with both beams. The purpose of this work is to verify the Doppler -Recoil formula proposed by Haugan and Kowalski. In the experiment performed, the resonant frequency of the stationary and moving velocity groups is determined using saturation spectroscopy. The theory predicts an average frequency shift of 307 Hz/^circC. The data show a shift of 94 kHz/^circ C. Because of the unexpected result, possible sources of errors such as pressure broadening, power broadening, and potential for systematic errors were examined. No explanation was found for these shifts.
Fu, Caixing; Yang, Min; Xiao, Songwen; Yang, Z
2016-01-01
We report that Hybrid membrane resonators (HMRs) made of a decorated membrane resonator backed by a shallow cavity can function as Helmholtz resonators (HRs) when mounted on the sidewall of a clear waveguide for air ventilation. When two single-frequency HMRs are used in the same scheme as two frequency-detuned HRs, asymmetric total absorption/reflection is demonstrated at 286.7 Hz with absorption coefficient over 97 % in a waveguide 9 cm x 9 cm in cross section. When two multiple-frequency HMRs are used, absorption in the range of near 60 % to above 80 % is observed at 403 Hz, 450 Hz, 688 Hz, 863 Hz and 945 Hz. Theoretical predictions agree well with the experimental data. The HMRs may replace HRs in duct noise reduction applications in that at a single operation frequency they have stronger strength to cover a much larger cross section area than that of HRs with similar cavity volume, and they can be designed to provide multiple frequency absorption band.
CFAVC scheme for high frequency series resonant inverter-fed domestic induction heating system
Nagarajan, Booma; Reddy Sathi, Rama
2016-01-01
This article presents the investigations on the constant frequency asymmetric voltage cancellation control in the AC-AC resonant converter-fed domestic induction heating system. Conventional fixed frequency control techniques used in the high frequency converters lead to non-zero voltage switching operation and reduced output power. The proposed control technique produces higher output power than the conventional fixed-frequency control strategies. In this control technique, zero-voltage-switching operation is maintained during different duty cycle operation for reduction in the switching losses. Complete analysis of the induction heating power supply system with asymmetric voltage cancellation control is discussed in this article. Simulation and experimental study on constant frequency asymmetric voltage cancellation (CFAVC)-controlled full bridge series resonant inverter is performed. Time domain simulation results for the open and closed loop of the system are obtained using MATLAB simulation tool. The simulation results prove the control of voltage and power in a wide range. PID controller-based closed loop control system achieves the voltage regulation of the proposed system for the step change in load. Hardware implementation of the system under CFAVC control is done using the embedded controller. The simulation and experimental results validate the performance of the CFAVC control technique for series resonant-based induction cooking system.
A robust adaptive load frequency control for micro-grids
DEFF Research Database (Denmark)
Khooban, Mohammad-Hassan; Niknam, Taher; Blaabjerg, Frede;
2016-01-01
The goal of this study is to introduce a novel robust load frequency control (LFC) strategy for micro-grid(s) (MG(s)) in islanded mode operation. Admittedly, power generators in MG(s) cannot supply steady electric power output and sometimes cause unbalance between supply and demand. Battery energy...... storage system (BESS) is one of the effective solutions to these problems. Due to the high cost of the BESS, a new idea of Vehicle-to-Grid (V2G) is that a battery of Electric-Vehicle (EV) can be applied as a tantamount large-scale BESS in MG(s). As a result, a new robust control strategy for an islanded......) controller. Implementing General Type II Fuzzy Systems is computationally expensive. However, using a recently introduced α-plane representation, GT2FLS can be seen as a composition of several Interval Type II Fuzzy Logic Systems (IT2FLS) with a corresponding level of α for each. Real-data from an offshore...
Four-channel magnetic resonance imaging receiver using frequency domain multiplexing
He, Wang; Qin, Xu; Jiejing, Ren; Gengying, Li
2007-01-01
An alternative technique that uses frequency domain multiplexing to acquire phased array magnetic resonance images is discussed in detail. The proposed method has advantages over traditional independent receiver chains in that it utilizes an analog-to-digital converter and a single-chip multicarrier receiver with high performance to reduce the size and cost of the phased array receiver system. A practical four-channel digital receiver using frequency domain multiplexing was implemented and verified on a home-built 0.3T magnetic resonance imaging system. The experimental results confirmed that the cross talk between each channel was below -60dB, the phase fluctuations were about 1°, and there was no obvious signal-to-noise ratio degradation. It is demonstrated that the frequency domain multiplexing is a valuable and economical technique, particularly for array coil systems where the multichannel receiver is indispensable and dynamic range is not a critical problem.
Estimation of body resonances from a time-frequency analysis of violin vibrato
Mellody, Maureen; Wakefield, Gregory H.
1999-11-01
We present a signal-based technique for evaluating a pole-zero representation of the resonant response of a violin instrument. This technique combines time-frequency signal analysis with system identification techniques to determine the pole-zero function that would account for amplitude modulation observed on the partials of violin notes performed with vibrato. Violin vibrato signals are analyzed with the modal distribution to obtain values of instantaneous amplitude and frequency for each partial. From these, input and output functions are synthesized and used to estimate the violin body's impulse response using an infinite impulse response (IIR) system identification procedure. In each case, the input and output functions share the same instantaneous frequency of the measured partial. However, the rapid amplitude variations are present only on the output function. We report on the location and spacing of these estimated resonances and discuss their relationship to those obtained from theoretical predictions and other measurement procedures.
High-frequency current oscillations in graphene-boron nitride resonant tunnel diodes
Greenaway, Mark; Gaskell, Jenn; Eaves, Laurence; Novoselov, Kostya; Mishchenko, Artem; Geim, Andre; Fromhold, Mark
The successful realisation of multilayer graphene-hBN-graphene resonant tunnelling diodes (graphene- RTDs) with negative differential conductance (NDC) and MHz current oscillations offers the exciting possibility of exploiting them as high-frequency oscillators and mixers. In this paper, we examine their potential for generating higher frequencies by simulating the oscillations in the tunnel current and charge that arise when the device is biased in the NDC region and placed in a resonant circuit. Using the Bardeen transfer Hamiltonian method, we examine the effect on the device characteristics of the twist angle, θ, between the two graphene electrodes, the hBN barrier thickness and of the carrier density in the graphene electrodes, which can be adjusted by chemical doping or by an applied bias voltage. The simulations accurately reproduce our recently-reported measurements on these RTDs (Fig. 4,). The results of simulations show that frequencies of tens of GHz are achievable by optimising the device parameters. Leverhulme Trust, UK.
Yakushin, Sergei B
2012-06-01
The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased and decreased in a side-down head orientation for 4 h in two cynomolgus monkeys. Adaptation was performed at 0.25, 1, 2, or 4 Hz. The gravity-dependent and -independent gain changes were determined over a range of head orientations from left-side-down to right-side-down at frequencies from 0.25 to 10 Hz, before and after adaptation. Gain changes vs. frequency data were fit with a Gaussian to determine the frequency at which the peak gain change occurred, as well as the tuning width. The frequency at which the peak gravity-dependent gain change occurred was approximately equal to the frequency of adaptation, and the width increased monotonically with increases in the frequency of adaptation. The gravity-independent component was tuned to the adaptive frequency of 0.25 Hz but was uniformly distributed over all frequencies when the adaptation frequency was 1-4 Hz. The amplitude of the gravity-independent gain changes was larger after the aVOR gain decrease than after the gain increase across all tested frequencies. For the aVOR gain decrease, the phase lagged about 4° for frequencies below the adaptation frequency and led for frequencies above the adaptation frequency. For gain increases, the phase relationship as a function of frequency was inverted. This study demonstrates that the previously described dependence of aVOR gain adaptation on frequency is a property of the gravity-dependent component of the aVOR only. The gravity-independent component of the aVOR had a substantial tuning curve only at an adaptation frequency of 0.25 Hz.
Flexible structured high-frequency film bulk acoustic resonator for flexible wireless electronics
International Nuclear Information System (INIS)
Flexible electronics have inspired many novel and very important applications in recent years and various flexible electronic devices such as diodes, transistors, circuits, sensors, and radiofrequency (RF) passive devices including antennas and inductors have been reported. However, the lack of a high-performance RF resonator is one of the key bottlenecks to implement flexible wireless electronics. In this study, for the first time, a novel ultra-flexible structured film bulk acoustic resonator (FBAR) is proposed. The flexible FBAR is fabricated on a flexible polyimide substrate using piezoelectric thin film aluminum nitride (AlN) for acoustic wave excitation. Both the shear wave and longitudinal wave can be excited under the surface interdigital electrodes configuration we proposed. In the case of the thickness extension mode, a flexible resonator with a working frequency as high as of 5.2325 GHz has been realized. The resonators stay fully functional under bending status and after repeated bending and re-flattening operations. This flexible high-frequency resonator will serve as a key building block for the future flexible wireless electronics, greatly expanding the application scope of flexible electronics. (paper)
International Nuclear Information System (INIS)
We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ∼4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ∼5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies
Chang, H.-C.; Kopaska-Merkel, D. C.; Chen, H.-C.; Rocky, Durrans S.
2000-01-01
Lithofacies identification supplies qualitative information about rocks. Lithofacies represent rock textures and are important components of hydrocarbon reservoir description. Traditional techniques of lithofacies identification from core data are costly and different geologists may provide different interpretations. In this paper, we present a low-cost intelligent system consisting of three adaptive resonance theory neural networks and a rule-based expert system to consistently and objectively identify lithofacies from well-log data. The input data are altered into different forms representing different perspectives of observation of lithofacies. Each form of input is processed by a different adaptive resonance theory neural network. Among these three adaptive resonance theory neural networks, one neural network processes the raw continuous data, another processes categorial data, and the third processes fuzzy-set data. Outputs from these three networks are then combined by the expert system using fuzzy inference to determine to which facies the input data should be assigned. Rules are prioritized to emphasize the importance of firing order. This new approach combines the learning ability of neural networks, the adaptability of fuzzy logic, and the expertise of geologists to infer facies of the rocks. This approach is applied to the Appleton Field, an oil field located in Escambia County, Alabama. The hybrid intelligence system predicts lithofacies identity from log data with 87.6% accuracy. This prediction is more accurate than those of single adaptive resonance theory networks, 79.3%, 68.0% and 66.0%, using raw, fuzzy-set, and categorical data, respectively, and by an error-backpropagation neural network, 57.3%. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.
Repetition rate multiplication of frequency comb using all-pass fiber resonator
Yang, Lijun; Yang, Honglei; Zhang, Hongyuan; Wei, Haoyun; Li, Yan
2016-09-01
We propose a stable method for repetition rate multiplication of a 250-MHz Er-fiber frequency comb by a phase-locked all-pass fiber ring resonator, whose phase-locking configuration is simple. The optical path length of the fiber ring resonator is automatically controlled to be accurately an odd multiple of half of the original cavity length using an electronical phase-locking unit with an optical delay line. As for shorter cavity length of the comb, high-order odd multiple is preferable. Because the power loss depends only on the net-attenuation of the fiber ring resonator, the energetic efficiency of the proposed method is high. The input and output optical spectrums show that the spectral width of the frequency comb is clearly preserved. Besides, experimental results show less pulse intensity fluctuation and 35 dB suppression ratio of side-modes while providing a good long-term and short-term frequency stability. Higher-order repetition rate multiplication to several GHz can be obtained by using several fiber ring resonators in cascade configuration.
Songer, Jocelyn E.; Eatock, Ruth Anne
2011-11-01
The mammalian saccule detects head tilt and low-frequency head accelerations as well as higher-frequency bone vibrations and sounds. It has two different hair cell types, I and II, dispersed throughout two morphologically distinct regions, the striola and extrastriola. Afferents from the two zones have distinct response dynamics which may arise partly from zonal differences in hair cell properties. We find that type II hair cells in the rat saccular epithelium adapt with a time course appropriate for influencing afferent responses to head motions. Moreover, striolar type II hair cells adapted by a greater extent than extrastriolar type II hair cells and had greater phase leads in the mid-frequency range (5-50 Hz). These differences suggest that hair cell transduction may contribute to zonal differences in the adaptation of vestibular afferents to head motions.
Frequency, amplitude, and phase measurements in contact resonance atomic force microscopies
Directory of Open Access Journals (Sweden)
Gheorghe Stan
2014-03-01
Full Text Available The resonance frequency, amplitude, and phase response of the first two eigenmodes of two contact-resonance atomic force microscopy (CR-AFM configurations, which differ in the method used to excite the system (cantilever base vs sample excitation, are analyzed in this work. Similarities and differences in the observables of the cantilever dynamics, as well as the different effect of the tip–sample contact properties on those observables in each configuration are discussed. Finally, the expected accuracy of CR-AFM using phase-locked loop detection is investigated and quantification of the typical errors incurred during measurements is provided.
Shinji Ito; Fuminori Hyodo
2016-01-01
Highly water-soluble ubiquinone-0 (CoQ0) reacts with ascorbate monoanion (Asc) to mediate the production of ascorbyl free radicals (AFR). Using aqueous reaction mixture of CoQ0 and Asc, we obtained positively enhanced dynamic nuclear polarization (DNP)-magnetic resonance (MR) images of the AFR at low frequency (ranging from 515 to 530 MHz) of electron spin resonance (ESR) irradiation. The shape of the determined DNP spectrum was similar to ESR absorption spectra with doublet spectral peaks. T...
Molecular dynamics study on a frequency-changeable nanotube cantilever resonator
Energy Technology Data Exchange (ETDEWEB)
Kang, Jeong Won; Choi, Young Gyu; Kim, Ki Sub [Chungju National University, Chungju (Korea, Republic of); Lee, Jun Ha [Sangmyung University, Chonan (Korea, Republic of); Song, Young Jin [Konyang University, Nonsan (Korea, Republic of); Hwang, Ho Jung [Chung-Ang National University, Seoul (Korea, Republic of)
2010-05-15
In this paper, the dynamics of a tunable resonator, which is based on the application of a telescoped multi-walled carbon nanotube that can be used repeatedly, is investigated via classical molecular dynamics simulations based on a double-walled carbon nanotube as the most simple multi-walled carbon nanotube. The fixed short outer nanotube rigidly confines the longer core nanotube, which can be freely telescoped. Such a system can tune its resonance frequency by controlling the length of the oscillating carbon nanotube.
Finite size effect on spread of resonance frequencies in arrays of coupled vortices
Energy Technology Data Exchange (ETDEWEB)
Vogel, Andreas; Drews, André; Im, Mi-Young; Fischer, Peter; Meier, Guido
2011-01-25
Dynamical properties of magnetic vortices in arrays of magnetostatically coupled ferromagnetic disks are studied by means of a broadband ferromagnetic-resonance (FMR) setup. Magnetic force microscopy and magnetic transmission soft X-ray microscopy are used to image the core polarizations and the chiralities which are both found to be randomly distributed. The resonance frequency of vortex-core motion strongly depends on the magnetostatic coupling between the disks. The parameter describing the relative broadening of the absorption peak observed in the FMR transmission spectra for a given normalized center-to-center distance between the elements is shown to depend on the size of the array.
Effect of Alfvén resonance on low-frequency fast wave current drive
Wang, C. Y.; Batchelor, D. B.; Carter, M. D.; Jaeger, E. F.; Stallings, D. C.
1995-08-01
The Alfvén resonances may occur on the low- and high-field sides for a low-frequency fast wave current drive scenario proposed for the International Thermonuclear Experimental Reactor (ITER) [Nucl. Fusion 31, 1135 (1991)]. At the resonance on the low-field side, the fast wave may be mode converted into a short-wavelength slow wave, which can be absorbed by electrons at the plasma edge, before the fast wave propagates into the core area of the plasma. Such absorption may cause a significant parasitic power loss.
Effect of Alfven resonance on low-frequency fast wave current drive
Energy Technology Data Exchange (ETDEWEB)
Wang, C.Y.; Batchelor, D.B.; Carter, M.D.; Jaeger, E.F.; Stallings, D.C. [Fusion Energy Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
1995-07-01
The Alfven resonances may occur on the low- and high-field sides for a low-frequency fast wave current drive scenario proposed for the International Thermonuclear Experimental Reactor (ITER) [Nucl. Fusion {bold 31}, 1135 (1991)]. At the resonance on the low-field side, the fast wave may be mode converted into a short-wavelength slow wave, which can be absorbed by electrons at the plasma edge, before the fast wave propagates into the core area of the plasma. Such absorption may cause a significant parasitic power loss. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Wagenaar, J J T; Donkersloot, R J; Marsman, F; de Wit, M; Bossoni, L; Oosterkamp, T H
2016-01-01
We present an innovative method for magnetic resonance force microscopy (MRFM) with ultra-low dissipation, by using the higher modes of the mechanical detector as radio frequency (rf) source. This method allows MRFM on samples without the need to be close to an rf source. Furthermore, since rf sources require currents that give dissipation, our method enables nuclear magnetic resonance experiments at ultra-low temperatures. Removing the need for an on-chip rf source is an important step towards a MRFM which can be widely used in condensed matter physics.
Two Novel Measurements for the Drive-Mode Resonant Frequency of a Micromachined Vibratory Gyroscope
Directory of Open Access Journals (Sweden)
Ancheng Wang
2013-11-01
Full Text Available To investigate the drive-mode resonance frequency of a micromachined vibratory gyroscope (MVG, one needs to measure it accurately and efficiently. The conventional approach to measure the resonant frequency is by performing a sweep frequency test and spectrum analysis. The method is time-consuming and inconvenient because of the requirements of many test points, a lot of data storage and off-line analyses. In this paper, we propose two novel measurement methods, the search method and track method, respectively. The former is based on the magnitude-frequency characteristics of the drive mode, utilizing a one-dimensional search technique. The latter is based on the phase-frequency characteristics, applying a feedback control loop. Their performances in precision, noise resistivity and efficiency are analyzed through detailed simulations. A test system is implemented based on a field programmable gate array (FPGA and experiments are carried out. By comparing with the common approach, feasibility and superiorities of the proposed methods are validated. In particular, significant efficiency improvements are achieved whereby the conventional frequency method consumes nearly 5,000 s to finish a measurement, while only 5 s is needed for the track method and 1 s for the search method.
Two novel measurements for the drive-mode resonant frequency of a micromachined vibratory gyroscope.
Wang, Ancheng; Hu, Xiaoping; Luo, Bing; Jiang, Mingming; He, Xiaofeng; Tang, Kanghua
2013-01-01
To investigate the drive-mode resonance frequency of a micromachined vibratory gyroscope (MVG), one needs to measure it accurately and efficiently. The conventional approach to measure the resonant frequency is by performing a sweep frequency test and spectrum analysis. The method is time-consuming and inconvenient because of the requirements of many test points, a lot of data storage and off-line analyses. In this paper, we propose two novel measurement methods, the search method and track method, respectively. The former is based on the magnitude-frequency characteristics of the drive mode, utilizing a one-dimensional search technique. The latter is based on the phase-frequency characteristics, applying a feedback control loop. Their performances in precision, noise resistivity and efficiency are analyzed through detailed simulations. A test system is implemented based on a field programmable gate array (FPGA) and experiments are carried out. By comparing with the common approach, feasibility and superiorities of the proposed methods are validated. In particular, significant efficiency improvements are achieved whereby the conventional frequency method consumes nearly 5,000 s to finish a measurement, while only 5 s is needed for the track method and 1 s for the search method.
Self-Oscillation-Based Frequency Tracking for the Drive and Detection of Resonance Magnetometers.
Tian, Zheng; Ren, Dahai; You, Zheng
2016-05-21
This paper reports a drive and detection method for Micro-Electro-Mechanical System (MEMS)-based Lorentz-force resonance magnetometers. Based on the proposed MEMS magnetometer, a drive and detection method was developed by using self-oscillation to adjust the mismatch between the mechanical resonance frequency and the coil drive frequency as affected by temperature fluctuations and vibration amplitude changes. Not only was the signal-to-noise ratio enhanced by the proposed method compared to the traditional method, but the test system automatically reached resonance frequency very rapidly when powered on. Moreover, the linearity and the measurement range were improved by the magnetic feedback generated by the coil. Test results indicated that the sensitivity of the proposed magnetometer is 59.6 mV/μT and its noise level is 0.25 μT. When operating in ±65 μT, its nonlinearity is 2.5‰-only one-tenth of the former prototype. Its power consumption is only about 250 mW and its size is only 28 mm × 28 mm × 10 mm, or about one-eighth of the original sensor; further, unlike the former device, it can distinguish both positive and negative magnetic fields. The proposed method can also be applied in other MEMS sensors such as gyroscopes and micromirrors to enhance their frequency tracking ability.
Krakover, Naftaly; Ilic, B. Robert; Krylov, Slava
2016-11-01
The ability to control nonlinear interactions of suspended mechanical structures offers a unique opportunity to engineer rich dynamical behavior that extends the dynamic range and ultimate device sensitivity. We demonstrate a displacement sensing technique based on resonant frequency monitoring of curved, doubly clamped, bistable micromechanical beams interacting with a movable electrode. In this configuration, the electrode displacement influences the nonlinear electrostatic interactions, effective stiffness and frequency of the curved beam. Increased sensitivity is made possible by dynamically operating the beam near the snap-through bistability onset. Various in-plane device architectures were fabricated from single crystal silicon and measured under ambient conditions using laser Doppler vibrometry. In agreement with the reduced order Galerkin-based model predictions, our experimental results show a significant resonant frequency reduction near critical snap-through, followed by a frequency increase within the post-buckling configuration. Interactions with a stationary electrode yield a voltage sensitivity up to ≈560 Hz V‑1 and results with a movable electrode allow motion sensitivity up to ≈1.5 Hz nm‑1. Our theoretical and experimental results collectively reveal the potential of displacement sensing using nonlinear interactions of geometrically curved beams near instabilities, with possible applications ranging from highly sensitive resonant inertial detectors to complex optomechanical platforms providing an interface between the classical and quantum domains.
Controlled degradation stochastic resonance in adaptive averaging cell-based architectures
Aymerich Capdevila, Nivard; Cotofana, Sorin; Rubio Sola, Jose Antonio
2013-01-01
In this paper, we first analyze the degradation stochastic resonance (DSR) effect in the context of adaptive averaging (AD-AVG) architectures. The AD-AVG is the adaptive version of the well-known AVG architecture . It is an optimized fault-tolerant design for future technologies with very high rates of failures and defects. With system degradation the AD-AVG reliability is diminishing, as expected, but at a certain moment in time it increases due to the DSR occurrence, which is counterintuiti...
Erni, Daniel; Liebig, Thorsten; Rennings, Andreas; Koster, Norbert H L; Fröhlich, Jürg
2011-01-01
We propose an adaptive RF antenna system for the excitation (and manipulation) of the fundamental circular waveguide mode (TE(11)) in the context of high-field (7T) traveling-wave magnetic resonance imaging (MRI). The system consists of composite right-/left-handed (CRLH) meta-material ring antennas that fully conforms to the inner surface of the MRI bore. The specific use of CRLH metamaterials is motivated by its inherent dispersion engineering capabilities, which is needed when designing resonant ring structures for virtually any predefined diameter operating at the given Larmor frequency (i.e. 298 MHz). Each functional group of the RF antenna system consists of a pair of subsequently spaced and correspondingly fed CRLH ring antennas, allowing for the unidirectional excitation of propagating, circularly polarized B(1) mode fields. The same functional group is also capable to simultaneously mold an incoming, counter-propagating mode. Given these functionalities we are proposing now a compound scheme (i.e. periodically arranged multiple antenna pairs)--termed as "MetaBore"--that is apt to provide a tailored RF power distribution as well as full wave reflection compensation virtually at any desired location along the bore.
Interocular transfer of spatial adaptation is weak at low spatial frequencies.
Baker, Daniel H; Meese, Tim S
2012-06-15
Adapting one eye to a high contrast grating reduces sensitivity to similar target gratings shown to the same eye, and also to those shown to the opposite eye. According to the textbook account, interocular transfer (IOT) of adaptation is around 60% of the within-eye effect. However, most previous studies on this were limited to using high spatial frequencies, sustained presentation, and criterion-dependent methods for assessing threshold. Here, we measure IOT across a wide range of spatiotemporal frequencies, using a criterion-free 2AFC method. We find little or no IOT at low spatial frequencies, consistent with other recent observations. At higher spatial frequencies, IOT was present, but weaker than previously reported (around 35%, on average, at 8c/deg). Across all conditions, monocular adaptation raised thresholds by around a factor of 2, and observers showed normal binocular summation, demonstrating that they were not binocularly compromised. These findings prompt a reassessment of our understanding of the binocular architecture implied by interocular adaptation. In particular, the output of monocular channels may be available to perceptual decision making at low spatial frequencies.
Institute of Scientific and Technical Information of China (English)
肖立民; 许希斌; 姚彦
2001-01-01
Diversity combining technologies are analyzed for fastfrequency-hopping spread spectrum systems during partial-band noise jamming to develop a novel combining receiver called an Adaptive Threshold Clipper Combining Receiver (ATCCR). The optimal clipping level for an ATCCR is analyzed, computed, and compared with several other diversity combining technologies. Since the ATCCR can estimate the power of the jamming and the number of jammed frequency cells to adaptively adjust the clipper's threshold, the system performance using the adaptive threshold clipper combining technique can be greatly improved.
Directory of Open Access Journals (Sweden)
Amit Banerjee
2012-09-01
Full Text Available Metallic nanocantilevers of gold are fabricated from self-supporting polycrystalline thin film (100 nm by focused ion beam assisted milling and ion induced manipulation processes. The surfactant assisted growth of the thin film leads to self-organized dendrite like morphology. This self-organized dendrite like morphology of the gold film imposes a new characteristic length scale corresponding to the mean size of gold grains present within the branches of the dendrite pattern in the film. The resonance characteristic investigated on cantilevers having different widths shows a significant drop in energy dissipation and hence an enhancement in the resonance amplitude at a characteristic width. At this width the resonance frequency of a vibrating cantilever approaches the theoretically expected value anticipated from an ideal cantilever treated like an elastic continuum.
Coherent Control of Ultra-High Frequency Acoustic Resonances in Photonic Crystal Fibers
Wiederhecker, G S; Fragnito, H L; Russell, P St J
2007-01-01
UHF (ultra-high frequency) acoustic resonances (~2 GHz) trapped within the glass core (1 micron diameter) of a photonic crystal fibre are excited electrostrictively using laser pulses of duration 100 ps and energy 500 pJ. Using precisely timed sequences of such driving pulses, we achieve coherent control of the acoustic resonances by constructive or destructive interference, demonstrating both enhancement and suppression of the vibrations. A sequence of resonantly-timed pulses (limited to 25 by the capacity of the erbium-doped fibre amplifier used) provides a 100-fold increase in the amplitude of the vibrational mode. The results are explained and interpreted using a semi-analytical theory, and supported by precise numerical simulations of the complex light-matter interaction.
Fabrication and Frequency Response Characteristics of AlN-Based Solidly Mounted Resonator
Institute of Scientific and Technical Information of China (English)
XIONG Juan; GU Hao-Shuang; HU Kuan; HU Ming-Zhe
2009-01-01
@@ Film bulk acoustic resonator (FBAR) with solidly mounted resonator (SMR)-type is carried out by rf magnetic sputtering. To fabricate SMR-type FBAR, alternative high and low acoustic impedance layers, Mo/Ti multilayer, are adopted as Bragg reflector deposited by dc magnetron sputtering. The influences of sputtering pressure, substrate temperature and sputtering power on the surface roughness of Bragg reflector layer are discussed. From the atom force microscopy (AFM) analysis, the surface roughness of the Bragg reflector is improved remarkably by controlling deposition conditions. Under the appropriate sputtering condition, AIN thin films with highly c-axis-preferred orientation are deposited by rf magnetron sputtering. The performance of fabricated Mo/Ti SMR shows that the electromechanical coupling coefficient is 3.89%, the series and parallel resonant frequencies appear at 2.49 and 2.53 GHz, with their quality factors 134.2 and 97.6, respectively.
Sadeqi, Soheil
The desire to reduce power consumption of current integrated circuits has led design engineers to focus on harvesting energy from free ambient sources such as vibrations. The energy harvested this way can eliminate the need for battery replacement, particularly, in low-energy remote sensing and wireless devices. Currently, most vibration-based energy harvesters are designed as linear resonators, therefore, they have a narrow resonance frequency. The optimal performance of such harvesters is achieved only when their resonance frequency is matched with the ambient excitation. In practice, however, a slight shift of the excitation frequency will cause a dramatic reduction in their performance. In the majority of cases, the ambient vibrations are totally random with their energy distributed over a wide frequency spectrum. Thus, developing techniques to extend the bandwidth of vibration-based energy harvesters has become an important field of research in energy harvesting systems. This thesis first reviews the broadband vibration-based energy harvesting techniques currently known in some detail with regard to their merits and applicability under different circumstances. After that, the design, fabrication, modeling and characterization of three new piezoelectric-based energy harvesting mechanism, built typically for rotary motion applications, is discussed. A step-by-step procedure is followed in order to broaden the bandwidth of such energy harvesters by introducing a coupled spring-mass system attached to a PZT beam undergoing rotary motion. It is shown that the new strategies can indeed give rise to a wide-band frequency response making it possible to fine-tune their dynamical response. The numerical results are shown to be in good agreement with the experimental data as far as the frequency response is concerned.
Low-distortion detection system for frequency-swept ion cyclotron resonance spectrometry
Wise, M. B.; Freiser, B. S.
1986-07-01
A high-performance frequency-swept capacitance bridge detector for ion cyclotron resonance (ICR) spectrometry has been constructed in our laboratory. Although the basic design of the system is similar to that of previously reported bridge circuits, careful design, layout, construction, and component selection have resulted in excellent frequency-swept performance over a bandwidth of 15 kHz to 1 MHz. At a magnetic field strength of 1.0 T, this corresponds to a mass range of 15-1000 Daltons. Problems with base-line drift and frequency-dependent signal distortion common to many other designs have been significantly reduced. Circuit diagrams are included for all parts of the detector and frequency response curves have been included where appropriate. In addition, several simple circuit diagrams for support devices have also been included.
Low-distortion detection system for frequency-swept ion cyclotron resonance spectrometry
Energy Technology Data Exchange (ETDEWEB)
Wise, M.B.; Freiser, B.S.
1986-07-01
A high-performance frequency-swept capacitance bridge detector for ion cyclotron resonance (ICR) spectrometry has been constructed in our laboratory. Although the basic design of the system is similar to that of previously reported bridge circuits, careful design, layout, construction, and component selection have resulted in excellent frequency-swept performance over a bandwidth of 15 kHz to 1 MHz. At a magnetic field strength of 1.0 T, this corresponds to a mass range of 15--1000 Daltons. Problems with base-line drift and frequency-dependent signal distortion common to many other designs have been significantly reduced. Circuit diagrams are included for all parts of the detector and frequency response curves have been included where appropriate. In addition, several simple circuit diagrams for support devices have also been included.
First Mode Schumann Resonance Frequency Variation During a Solar Proton Event
Directory of Open Access Journals (Sweden)
Minu Sanfui
2016-04-01
Full Text Available A severe X-ray flare occurred on 06 - 07 March 2012 followed by a solar proton event (SPE. During this event we studied the variation in frequency of the first Schumann resonance (SR spectra mode from the recorded data over Kolkata (22.56°N, 88.5°E. The first mode frequency enhanced (~8.14 Hz, 3.85% during the solar X-ray bursts and immediately after its value decreased (~7.44 Hz, 5.13% during the proton event. The influences of SPE and X-ray bursts upon the SR frequency fluctuation are explained in terms of the changes in medium ionization, i.e., the change in dielectric property and two layer reflection height variation in the waveguide. The geomagnetic storm effect on the modification of this frequency variation occurring during that time is also considered.
Inverse Bloch-oscillator: Strong Thz-photocurrent resonances at the Bloch frequency
Energy Technology Data Exchange (ETDEWEB)
Unterrainer, K.; Keay, B.J.; Wanke, M.C. [Univ. of California, Santa Barbara, CA (United States)] [and others
1995-12-31
We have observed resonant changes in the current-voltage characteristics of miniband semiconductor superlattices when the Bloch frequency is resonant with a terahertz field and its harmonics: the inverse Bloch oscillator effect. The resonant feature consists of a peak in the current which grows with increasing laser intensity accompanied by a decrease of the current at the low bias side. The peak position moves linearly with the laser frequency. When the intensity is increased further the first peak starts to decrease and a second peak at about twice the voltage of the first peak is observed due to a two photon resonance. At the highest intensities we observe up to a four photon resonance. A superlattice is expected to show negative differential conductance due to the strong nonparabolicity of the miniband. In this situation the carriers should undergo Bloch oscillations with a frequency {omega}{sub B} = eEd/h. Transient Bloch oscillations of photo excited carriers have been observed in time resolved Thz emission measurements. However, the possibility of Thz generation form a DC voltage biased superlattice is still under discussion. We have approached this problem by exploring the inverse Bloch oscillator effect in a superlattice excited by the Thz radiation form the UCSB FEL. The superlattice consists of 40 periods of 80{angstrom} GaAs wells and 20{angstrom} Al{sub 0.3}Ga{sub 0.7}As barriers. To couple the electric field of the Terahertz radiation parallel to the growth direction a coplanar bowtie antenna has been employed. Our results show clearly that the external radiation couples to Bloch oscillations in contrary to theoretical suggestions that Thz radiation would not couple to a uniform Wannier Stark ladder. We conclude that this result is intimately related to dissipation and line broadening of the otherwise identical states in the ladder: absorption appears above the Wannier Stark splitting ({omega}{sub B}<{omega}) and gain below ({omega}{sub B}>{omega}).
Tadesse, Semere Ayalew
2014-01-01
Light-sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally these devices operate in megahertz frequency range where the acoustic wavelength is much longer than the optical wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, acoustic waves with sub-optical wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10 GHz with the acoustic wavelength significantly below the optical wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct...
Optical frequency comb generation from aluminum nitride micro-ring resonator
Jung, Hojoong; Fong, King Y; Zhang, Xufeng; Tang, Hong X
2013-01-01
Aluminum nitride is an appealing nonlinear optical material for on-chip wavelength conversion. Here we report optical frequency comb generation from high quality factor aluminum nitride micro-ring resonators integrated on silicon substrates. By engineering the waveguide structure to achieve near-zero dispersion at telecommunication wavelengths and optimizing the phase matching for four-wave mixing, frequency combs are generated with a single wavelength continuous-wave pump laser. The Kerr coefficient (n2) of aluminum nitride is further extracted from our experimental results.
Time-of-flight detection of ultra-cold atoms using resonant frequency modulation imaging.
Hardman, K S; Wigley, P B; Everitt, P J; Manju, P; Kuhn, C C N; Robins, N P
2016-06-01
Resonant frequency modulation imaging is used to detect free falling ultra-cold atoms. A theoretical comparison of fluorescence imaging (FI) and frequency modulation imaging (FMI) is made, indicating that for low optical depth clouds, FMI accomplished a higher signal-to-noise ratio under conditions necessary for a 200 μm spatially resolved atom interferometer. A 750 ms time-of-flight measurement reveals near atom shot-noise limited number measurements of 2×106 Bose-condensed Rb87 atoms. The detection system is applied to high precision spinor BEC based atom interferometer. PMID:27244400
Tung, J. C.; Tuan, P. H.; Liang, H. C.; Huang, K. F.; Chen, Y. F.
2016-08-01
We theoretically verify that the symmetry breaking in spherical resonators can result in a fractal frequency spectrum that is full of numerous new accidental degeneracies to cluster around the unperturbed degenerate cavity. We further experimentally discover that the fractal frequency spectrum excellently reflects the intimate connection between the emission power and the degenerate mode numbers. It is observed that the wave distributions of lasing modes at the accidental degeneracies are strongly concentrated on three-dimensional (3D) geometric topology. Considering the overlapping effect, the wave representation of the coherent states is analytically derived to manifest the observed 3D geometric surfaces.
Microwave and RF applications for micro-resonator based frequency combs
Nguyen, Thach G.; Shoeiby, Mehrdad; Ferrera, Marcello; Pasquazi, Alessia; Peccianti, Marco; Chu, Sai T.; Little, Brent E.; Morandotti, Roberto; Mitchell, Arnan; Moss, David J.
2016-02-01
Photonic integrated circuits that exploit nonlinear optics in order to generate and process signals all-optically have achieved performance far superior to that possible electronically - particularly with respect to speed. We review the recent achievements based in new CMOS-compatible platforms that are better suited than SOI for nonlinear optics, focusing on radio frequency (RF) and microwave based applications that exploit micro-resonator based frequency combs. We highlight their potential as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We review recent work on a photonic RF Hilbert transformer for broadband microwave in-phase and quadrature-phase generation based on an integrated frequency optical comb. The comb is generated using a nonlinear microring resonator based on a CMOS compatible, high-index contrast, doped-silica glass platform. The high quality and large frequency spacing of the comb enables filters with up to 20 taps, allowing us to demonstrate a quadrature filter with more than a 5-octave (3 dB) bandwidth and an almost uniform phase response.
International Nuclear Information System (INIS)
Within the framework of a sequential quantum mechanical model, the response and the power of a coherent generation have been obtained numerically in a resonant-tunneling diode in a wide range of frequencies with the electron-electron interaction. The quantum regime of generation is shown to be sustained under the electron-electron interaction. Thus, a high-power generation is probable under frequencies exceeding the width of the resonant level
Institute of Scientific and Technical Information of China (English)
Shi-Qi Jiang; Bo Wu; Tian-Xiang Gu
2007-01-01
The stochastic resonance phenomenon in a harmonic oscillator with fluctuating intrinsic frequency by asymmetric dichotomous noise is investigated in this paper By using the random average method and ShapiroLoginov formula, the exact solution of the average output amplitude gain (OAG) is obtained. Numerical results show that OAG depends nonmonotonically on the noise characteristics: intensity, correlation time and asymmetry.The maximum OAG can be achieved by tuning the noise asymmetry and or the noise correlation time.
International Nuclear Information System (INIS)
The achievement of low resonance frequency in vertical action oscillators is the most difficult of the basic ingredients for seismic noise attenuation filters. These oscillations are achieved by means of 'anti-springs' systems coupled with more classical suspension springs. Magnetic anti-springs have been used so far. Geometric anti-springs have been studied and the concept tested in this work, opening the way to a simpler and better performance seismic attenuation filters. (author)
High Frequency Resonance Damping of DFIG based Wind Power System under Weak Network
DEFF Research Database (Denmark)
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2016-01-01
in the Rotor Side Converter (RSC) or in the Grid Side Converter (GSC), through the introduction of virtual positive capacitor or virtual negative inductor to reshape the DFIG system impedance and mitigate the high frequency resonance. A detailed theoretical explanation on the virtual positive...... capacitor or virtual negative inductor has been given, and their parameters are also optimally designed. The proposed DFIG system damping control strategy has been validated by experimental results....
Mehran Shokri; Arash Daraeighadikolaei
2013-01-01
Background. There is no doubt that the success of the dental implants depends on the stability. The aim of this work was to measure the stability of dental implants prior to loading the implants, using a resonance frequency analysis (RFA) by Osstell mentor device. Methods. Ten healthy and nonsmoker patients over 40 years of age with at least six months of complete or partial edentulous mouth received screw-type dental implants by a 1-stage procedure. RFA measurements were obtained at surgery ...
A Simplified Analytical Technique for High Frequency Characterization of Resonant Tunneling Diode
DESSOUKI, A. A. S.; ABDALLAH, R. M.; Aly, M.H.
2014-01-01
his paper proposes a simplified analytical technique for high frequency characterization of the resonant tunneling diode (RTD). An equivalent circuit of the RTD that consists of a parallel combination of conductance, G (V, f), and capacitance, C (V, f) is formulated. The proposed approach uses the measured DC current versus voltage characteristic of the RTD to extract the equivalent circuit elements parameters in the entire bias range. Using the proposed analytical technique, ...
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
This letter presents a multi-frequency proportional-resonant (MFPR) current controller developed for PWM voltage source converter (VSC) under the unbalanced supply voltage conditions. The delta operator is used in place of the shift operator for the implementation of MFPR by using a low-cost fixed-point DSP. The experimental results with an alternative control strategy validated the feasibility of the proposed MFPR current controller for the PWM VSC during voltage unbalance.
Institute of Scientific and Technical Information of China (English)
Ke TANG; Tian LEI; Xiao-gang LIN; Tao JIN; Yu ZHANG
2011-01-01
Gas-liquid coupling oscillation is a novel approach to reducing the resonant frequency and to elevating the pressure amplitude of a thermoacoustic engine. If a thermoacoustic engine is used to drive low-frequency pulse tube refrigerators, the frequency matching between the thermoacoustic engine and the refrigerator plays an important role. Based on an acoustic-electric analogy, a lumped parameter model is proposed to estimate the resonant frequency of a standing-wave thermoacoustic engine with gas-liquid coupling oscillation. Furthermore, a simplified lumped parameter model is also developed to reduce the computation complexity. The resonant frequency dependence on the mean pressure, the gas space volume, and the water column length is computed and analyzed. The impact of different working gases on the resonant frequency is also discussed. The effectiveness of the models is validated by comparing the computed results with the experimental data of the gas-liquid coupling oscillation system. An increase in the mean working pressure can lead to a rise in the resonant frequency, and a lower resonant frequency can be achieved by elongating the liquid column. In comparison with nitrogen and argon, carbon dioxide can realize a lower frequency due to a smaller specific heat ratio.
Institute of Scientific and Technical Information of China (English)
Ji Wang; Yu Wang; Wenke Hu; Wenhua Zhao; Jianke Du; Dejin Huang
2008-01-01
Quartz crystal resonators are typical piezoelectric acoustic wave devices for frequency control applications with mechanical vibration frequency at the radio-frequency (RF) range. Precise analyses of the vibration and deformation are generally required in the resonator design and improvement process. The considerations include the presence of electrodes, mountings, bias fields such as temperature, initial stresses, and acceleration. Naturally, the finite element method is the only effective tool for such a coupled problem with multi-physics nature. The main challenge is the extremely large size of resulted linear equations. For this reason, we have been employing the Mindlin plate equations to reduce the computational difficulty. In addition, we have to utilize the parallel computing techniques on Linux clusters, which are widely available for academic and industrial applications nowadays, to improve the computing efficiency. The general principle of our research is to use open source software components and public domain technology to reduce cost for developers and users on a Linux cluster. We start with a mesh generator specifically for quartz crystal resonators of rectangular and circular types, and the Mindlin plate equations are implemented for the finite element analysis. Computing techniques like parallel processing, sparse matrix handling, and the latest eigenvalue extraction package are integrated into the program. It is clear from our computation that the combination of these algorithms and methods on a cluster can meet the memory requirement and reduce computing time significantly.
Zhang, Wen-Ming; Yan, Han; Jiang, Hui-Ming; Hu, Kai-Ming; Peng, Zhi-Ke; Meng, Guang
2016-04-01
In this paper, the dynamics of suspended microchannel resonators which convey internal flows with opposite directions are investigated. The fluid-structure interactions between the laminar fluid flow and oscillating cantilever are analyzed by comprehensively considering the effects of velocity profile, flow viscosity and added flowing particle. A new model is developed to characterize the dynamic behavior of suspended microchannel resonators with the fluid-structure interactions. The stability, frequency shift and energy dissipation of suspended microchannel resonators are analyzed and discussed. The results demonstrate that the frequency shifts induced by the added flowing particle which are obtained from the new model have a good agreement with the experimental data. The steady mean flow can cause the frequency shift and influence the stability of the dynamic system. As the flow velocity reaches the critical value, the coupled-mode flutter occurs via a Hamiltonian Hopf bifurcation. The perturbation flow resulted from the vibration of the microcantilever leads to energy dissipation, while the steady flow does not directly cause the damping which increases with the increasing of the flow velocity predicted by the classical model. It can also be found that the steady flow firstly changes the mode shape of the cantilever and consequently affects the energy dissipation.
Decentralized & Adaptive Load-Frequency Control Scheme of Variable Speed Wind Turbines
DEFF Research Database (Denmark)
Hoseinzadeh, Bakhtyar; Silva, Filipe Miguel Faria da; Bak, Claus Leth
2014-01-01
and therefore determining the contribution factor of each individual WT to gain an adaptive LFC approach. The Electrical Distance (ED) concept confirms that the locally measured voltage decay is a proper criterion of closeness to the disturbance place. Numerical simulations carried out in DigSilent Power......In power systems with high penetration of Wind Power (WP), transferring a part of Load Frequency Control (LFC) burden to variable speed Wind Turbines (WTs) is inevitable. The conventional LFC schemes merely rely on frequency information and since frequency is a common variable throughout......Factory software confirm the efficiency of proposed methodology to stabilize the power system after a severe contingency....
On frequency domain adaptive filters using the overlap-add method
Sommen, P.C.W.; Jayasinghe, J.A.K.S.
1988-01-01
The authors introduce a frequency-domain adaptive filter (FDAF) configuration using the overlap-add method which has the same complexity and convergence behavior as the overlap-save configuration. It is shown that an FDAF using the overlap-add method can be realized with the same number of DFTs (dis
Directory of Open Access Journals (Sweden)
Jinbao Yao
2016-01-01
Full Text Available Shock pulse method is a widely used technique for condition monitoring of rolling bearing. However, it may cause erroneous diagnosis in the presence of strong background noise or other shock sources. Aiming at overcoming the shortcoming, a pulse adaptive time-frequency transform method is proposed to extract the fault features of the damaged rolling bearing. The method arranges the rolling bearing shock pulses extracted by shock pulse method in the order of time and takes the reciprocal of the time interval between the pulse at any moment and the other pulse as all instantaneous frequency components in the moment. And then it visually displays the changing rule of each instantaneous frequency after plane transformation of the instantaneous frequency components, realizes the time-frequency transform of shock pulse sequence through time-frequency domain amplitude relevancy processing, and highlights the fault feature frequencies by effective instantaneous frequency extraction, so as to extract the fault features of the damaged rolling bearing. The results of simulation and application show that the proposed method can suppress the noises well, highlight the fault feature frequencies, and avoid erroneous diagnosis, so it is an effective fault feature extraction method for the rolling bearing with high time-frequency resolution.
Carbon Nanofiber-Based, High-Frequency, High-Q, Miniaturized Mechanical Resonators
Kaul, Anupama B.; Epp, Larry W.; Bagge, Leif
2011-01-01
High Q resonators are a critical component of stable, low-noise communication systems, radar, and precise timing applications such as atomic clocks. In electronic resonators based on Si integrated circuits, resistive losses increase as a result of the continued reduction in device dimensions, which decreases their Q values. On the other hand, due to the mechanical construct of bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators, such loss mechanisms are absent, enabling higher Q-values for both BAW and SAW resonators compared to their electronic counterparts. The other advantages of mechanical resonators are their inherently higher radiation tolerance, a factor that makes them attractive for NASA s extreme environment planetary missions, for example to the Jovian environments where the radiation doses are at hostile levels. Despite these advantages, both BAW and SAW resonators suffer from low resonant frequencies and they are also physically large, which precludes their integration into miniaturized electronic systems. Because there is a need to move the resonant frequency of oscillators to the order of gigahertz, new technologies and materials are being investigated that will make performance at those frequencies attainable. By moving to nanoscale structures, in this case vertically oriented, cantilevered carbon nanotubes (CNTs), that have larger aspect ratios (length/thickness) and extremely high elastic moduli, it is possible to overcome the two disadvantages of both bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators. Nano-electro-mechanical systems (NEMS) that utilize high aspect ratio nanomaterials exhibiting high elastic moduli (e.g., carbon-based nanomaterials) benefit from high Qs, operate at high frequency, and have small force constants that translate to high responsivity that results in improved sensitivity, lower power consumption, and im - proved tunablity. NEMS resonators have recently been demonstrated using topdown
Dhurjaty, Sreeram; Qiu, Yuchen; Tan, Maxine; Zheng, Bin
2014-03-01
Electrical Impedance Spectroscopy (EIS) has shown promising results for differentiating between malignant and benign tumors, which exhibit different dielectric properties. However, the performance of current EIS systems has been inadequate and unacceptable in clinical practice. In the last several years, we have been developing and testing a new EIS approach using resonance frequencies for detection and classification of suspicious tumors. From this experience, we identified several limitations of current technologies and designed a new EIS system with a number of new characteristics that include (1) an increased A/D (analog-to-digital) sampling frequency, 24 bits, and a frequency resolution of 100 Hz, to increase detection sensitivity (2) automated calibration to monitor and correct variations in electronic components within the system, (3) temperature sensing and compensation algorithms to minimize impact of environmental change during testing, and (4) multiple inductor-switching to select optimum resonance frequencies. We performed a theoretical simulation to analyze the impact of adding these new functions for improving performance of the system. This system was also tested using phantoms filled with variety of liquids. The theoretical and experimental test results are consistent with each other. The experimental results demonstrated that this new EIS device possesses the improved sensitivity and/or signal detection resolution for detecting small impedance or capacitance variations. This provides the potential of applying this new EIS technology to different cancer detection and diagnosis tasks in the future.
Generation of THz frequency using PANDA ring resonator for THz imaging
Directory of Open Access Journals (Sweden)
Ong CT
2012-02-01
Full Text Available MA Jalil1, Afroozeh Abdolkarim2, T Saktioto2, CT Ong3, Preecha P Yupapin41Ibnu Sina Institute of Fundamental Science Studies, Nanotechnology Research Alliance, Universiti Teknologi Malaysia (UTM,81310, Johor Bahru, Malaysia; 2Institute of Advanced Photonics Science, Nanotechnology Research Alliance, Universiti Teknologi Malaysia (UTM, 81310, Johor Bahru, Malaysia; 3Department of Mathematics, Universiti Teknologi Malaysia 81310 Skudai, Johor Bahru, Malaysia; 4Nanoscale Science and Engineering Research Alliance (N'SERA, Advanced Research Center for Photonics, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, ThailandAbstract: In this study, we have generated terahertz (THz frequency by a novel design of microring resonators for medical applications. The dense wavelength-division multiplexing can be generated and obtained by using a Gaussian pulse propagating within a modified PANDA ring resonator and an add/drop filter system. Our results show that the THz frequency region can be obtained between 40–50 THz. This area of frequency provides a reliable frequency band for THz pulsed imaging.Keywords: THz imaging, THz technology, MRRs, PANDA, add/drop filter
Recent developments in phyroshock simulation using fixtures with tunable resonant frequencies
Energy Technology Data Exchange (ETDEWEB)
Davie, N.T.; Bateman, V.I.
1994-02-01
Pyroshock is a potentially severe environment produced by the detonation of explosively actuated components and stage separation hardware. Electronic components exposed to pyroshock events during flight or deployment can be damaged by this high frequency, high G shock. Flight qualification of these components may be accomplished using one of many existing techniques to simulate the pyroshock environment in the laboratory. Two new techniques developed at Sandia National Laboratories allow larger components to be tested to a wide variety of pyroshock environments. The frequency content and amplitude of the simulated pyroshock can be easily controlled in a predictable manner. The pyroshock environment is produced by the resonant response of a test fixture that has been excited by a mechanical impact. The resonant fixture has a dominant frequency that can be continuously adjusted over a frequency range that is typically found in most pyroshock environments. The test apparatus and techniques utilized by each method will be described in this paper. Experimental results will be presented which illustrate the capabilities of each method.
Capabilities, performance, and future possibilities of high frequency polyphase resonant converters
International Nuclear Information System (INIS)
High Frequency Polyphase Resonant Power Conditioning (PRPC) techniques developed at Los Alamos National Laboratory (LANL) are now being utilized for the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS) accelerator klystron RF amplifier power systems. Three different styles of polyphase resonant converter modulators were developed for the SNS application. The various systems operate up to 140 kV, or 11 MW pulses, or up to 1.1 MW average power, all from a DC input of +/- 1.2 kV. Component improvements realized with the SNS effort coupled with new applied engineering techniques have resulted in dramatic changes in RF power conditioning topology. As an example, the high-voltage transformers are over 100 times smaller and lighter than equivalent 60 Hz versions. With resonant conversion techniques, load protective networks are not required. A shorted load de-tunes the resonance and little power transfer can occur. This provides for power conditioning systems that are inherently self-protective, with automatic fault 'ride-through' capabilities. By altering the Los Alamos design, higher power and CW power conditioning systems can be realized without further demands of the individual component voltage or current capabilities. This has led to designs that can accommodate 30 MW long pulse applications and megawatt class CW systems with high efficiencies. The same PRPC techniques can also be utilized for lower average power systems (∼250 kW). This permits the use of significantly higher frequency conversion techniques that result in extremely compact systems with short pulse (10 to 100 us) capabilities. These lower power PRPC systems may be suitable for medical Linacs and mobile RF systems. This paper will briefly review the performance achieved for the SNS accelerator and examine designs for high efficiency megawatt class CW systems and 30 MW peak power applications. The devices and designs for compact higher frequency converters utilized for short pulse
Directory of Open Access Journals (Sweden)
Yun Wang
2015-06-01
Full Text Available This article conceptually proposes a new method to tune the resonance frequency of piezoelectric vibration energy harvesters, in which the supporting position of the vibrator can be adjusted for frequency tuning. The corresponding analytical model is established to predict the performances of the harvester based on the principles of energy. First, the equivalent stiffness and mass of the vibrator in bending mode are derived explicitly for the different supporting positions. A simple analysis method is then established for the frequency, output voltage, and output power. Finally, some numerical examples are given to demonstrate the presented method. The results are also compared with those by finite element method and good agreement is observed.
Observation of resonant energy transfer between identical-frequency laser beams
Energy Technology Data Exchange (ETDEWEB)
Afeyan, B. B.; Cohen, B. I.; Estabrook, K. G.; Glenzer, S. H.; Joshi, C.; Kirkwood, R. K.; Moody, J. D.; Wharton, K. B.
1998-12-09
Enhanced transmission of a low intensity laser beam is observed when crossed with an identical-frequency beam in a plasma with a flow velocity near the ion sound speed. The time history of the enhancement and the dependence on the flow velocity strongly suggest that this is due to energy transfer between the beams via a resonant ion wave with zero frequency in the laboratory frame. The maximum energy transfer has been observed when the beams cross in a region with Mach 1 flow. The addition of frequency modulation on the crossing beams is seen to reduce the energy transfer by a factor of two. Implications for indirect-drive fusion schemes are discussed.
Frequency Tuning Study on Half-wave Resonator for China ADS in IMP
He, Shoubo; Yue, Weiming; Zhang, Cong; Zhang, Shenghu; Zhao, Hongwei
2013-01-01
Within the framework of the China Accelerator Driven Sub-critical System (CADS) project, a 162.5MHz superconducting half-wave resonator (HWR) for low energy section of high power proton linac promoted by Institute of Modern Physics (IMP) is under development. For the geometrical design of superconducting cavities, the RF and mechanical coupled analysis are essential to predict the deformation of the cavity walls and the frequency detuning. Bath helium pressure and Lorentz force detuning effect for the HWR cavity are presented in this paper. Tuning system has been investigated to control the frequency shift perturbed by changing the distance along the beam axis of the cavity. The simulation results performed with ANSYS code show the tuning system can adjust and compensate the frequency drift of cavity due to external vibrations and fluctuation during operation.
High-frequency resonant tunnelling diode oscillator with high-output power
Wang, Jue; Alharbi, Khalid; Ofiare, Afesomeh; Khalid, Ata; Cumming, David; Wasige, Edward
2015-10-01
In this paper, a prototype G-band (140 GHz-220 GHz) monolithic microwave integrated circuit (MMIC) resonant tunneling diode (RTD) oscillator is reported. The oscillator employs two In0.53Ga0.47As/AlAs RTD devices in the circuit to increase the output power. The measured output power was about 0.34 mW (-4.7 dBm) at 165.7 GHz, which is the highest power reported for RTD oscillator in G-band frequency range. This result demonstrates the validity of the high frequency/high power RTD oscillator design. It indicates that RTD devices, as one of the terahertz (THz) source candidates, have promising future for room-temperature THz applications in such as imaging, wireless communication and spectroscopy analysis, etc. By optimizing RTD oscillator design, it is expected that considerably higher power (>1 mW) at THz frequencies (>300 GHz) will be obtained.
The mass load effect on the resonant acoustic frequencies of colloidal semiconductor nanoplatelets
Girard, Adrien; Saviot, Lucien; Pedetti, Silvia; Tessier, Mickaël D.; Margueritat, Jérémie; Gehan, Hélène; Mahler, Benoit; Dubertret, Benoit; Mermet, Alain
2016-07-01
Resonant acoustic modes of ultrathin CdS and CdSe colloidal nanoplatelets (NPLs) with varying thicknesses were probed using low frequency Raman scattering. The spectra are dominated by an intense band ascribed to the thickness breathing mode of the 2D nanostructures. The measured Raman frequencies show strong deviations with respect to the values expected for simple bare plates, all the more so as the thickness is reduced. The deviation is shown to arise from the additional mass of the organic ligands that are bound to the free surfaces of the nanoplatelets. The calculated eigen frequencies of vibrating platelets weighed down by the mass of the organic ligands are in very good agreement with the observed experimental behaviours. This finding opens up a new possibility of nanomechanical sensing such as nanobalances.Resonant acoustic modes of ultrathin CdS and CdSe colloidal nanoplatelets (NPLs) with varying thicknesses were probed using low frequency Raman scattering. The spectra are dominated by an intense band ascribed to the thickness breathing mode of the 2D nanostructures. The measured Raman frequencies show strong deviations with respect to the values expected for simple bare plates, all the more so as the thickness is reduced. The deviation is shown to arise from the additional mass of the organic ligands that are bound to the free surfaces of the nanoplatelets. The calculated eigen frequencies of vibrating platelets weighed down by the mass of the organic ligands are in very good agreement with the observed experimental behaviours. This finding opens up a new possibility of nanomechanical sensing such as nanobalances. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR07383A
A Simplified Analytical Technique for High Frequency Characterization of Resonant Tunneling Diode
Directory of Open Access Journals (Sweden)
DESSOUKI, A. A. S.
2014-11-01
Full Text Available his paper proposes a simplified analytical technique for high frequency characterization of the resonant tunneling diode (RTD. An equivalent circuit of the RTD that consists of a parallel combination of conductance, G (V, f, and capacitance, C (V, f is formulated. The proposed approach uses the measured DC current versus voltage characteristic of the RTD to extract the equivalent circuit elements parameters in the entire bias range. Using the proposed analytical technique, the frequency response - including the high frequency range - of many characteristic aspects of the RTD is investigated. Also, the maximum oscillation frequency of the RTD is calculated. The results obtained have been compared with those concluded and reported in the literature. The reported results in literature were obtained through simulation of the RTD at high frequency using either a computationally complicated quantum simulator or through difficult RF measurements. A similar pattern of results and highly concordant conclusion are obtained. The proposed analytical technique is simple, correct, and appropriate to investigate the behavior of the RTD at high frequency. In addition, the proposed technique can be easily incorporated into SPICE program to simulate circuits containing RTD.
Schuengel, Edmund; Korolov, Ihor; Derzsi, Aranka; Donko, Zoltan; Schulze, Julian
2016-01-01
The self-excitation of plasma series resonance (PSR) oscillations is a prominent feature in the current of low pressure capacitive radio frequency (RF) discharges. This resonance leads to high frequency oscillations of the charge in the sheaths and enhances electron heating. Up to now, the phenomenon has only been observed in asymmetric discharges. There, the nonlinearity in the voltage balance, which is necessary for the self-excitation of resonance oscillations with frequencies above the applied frequencies, is caused predominantly by the quadratic contribution to the charge-voltage relation of the plasma sheaths. Using PIC/MCC simulations of single- and multi- frequency capacitive discharges and an equivalent circuit model, we demonstrate that other mechanisms such as a cubic contribution to the charge-voltage relation of the plasma sheaths and the time dependent bulk electron plasma frequency can cause the self-excitation of PSR oscillations, as well. These mechanisms have been neglected in previous model...
Kotrlova, Andrea; Torok, Gabriel
2013-01-01
The multi-resonance orbital model of high-frequency quasi-periodic oscillations (HF QPOs) enables precise determination of the black hole dimensionless spin a if observed set of oscillations demonstrates three (or more) commensurable frequencies. The black hole spin is related to the frequency ratio only, while its mass M is related to the frequency magnitude. The model is applied to the triple frequency set of HF QPOs observed in Sgr A* source with frequency ratio 3:2:1. Acceptable versions of the multi-resonance model are determined by the restrictions on the Sgr A* supermassive black hole mass. Among the best candidates the version of strong resonances related to the black hole "magic" spin a=0.983 belongs. However, the version demonstrating the best agreement with the mass restrictions predicts spin a=0.980.
Polymer waveguide Fabry-Perot resonator for high-frequency ultrasound detection.
Tadayon, Mohammad Amin; Baylor, Martha-Elizabeth; Ashkenazi, Shai
2014-12-01
Piezoelectric technology is the backbone of most medical ultrasound imaging arrays; however, signal transduction efficiency severely deteriorates in scaling the technology to element size smaller than 0.1 mm, often required for high-frequency operation (>20 MHz). Optical sensing and generation of ultrasound has been proposed and studied as an alternative technology for implementing sub-millimeter size arrays with element size down to 10 μm. The application of thin polymer film Fabry-Perot resonators has been demonstrated for high-frequency ultrasound detection; however, their sensitivity is limited by light diffraction loss. Here, we introduce a new method to increase the sensitivity of an optical ultrasound receiver by utilizing a waveguide between the mirrors of the Fabry-Perot resonator. This approach eliminates diffraction loss from the cavity, and therefore the finesse is only limited by mirror loss and absorption. By applying this method, we have achieved noise equivalent pressure of 178 Pa over a bandwidth of 30 MHz or 0.03 Pa/Hz1/2, which is about 20-fold better than a similar device without a waveguide. The finesse of the tested Fabry-Perot resonator was around 200. This result is 5 times higher than the finesse measured in the same device outside the waveguide region.
All-dielectric frequency selective surface design based on dielectric resonator
Zheng-Bin, Wang; Chao, Gao; Bo, Li; Zhi-Hang, Wu; Hua-Mei, Zhang; Ye-Rong, Zhang
2016-06-01
In this work, we propose an all-dielectric frequency selective surface (FSS) composed of periodically placed high-permittivity dielectric resonators and a three-dimensional (3D) printed supporter. Mie resonances in the dielectric resonators offer strong electric and magnetic dipoles, quadrupoles, and higher order terms. The re-radiated electric and magnetic fields by these multipoles interact with the incident fields, which leads to total reflection or total transmission in some special frequency bands. The measured results of the fabricated FSS demonstrate a stopband fractional bandwidth (FBW) of 22.2%, which is consistent with the simulated result. Project supported by the National Natural Science Foundation of China (Grant Nos. 61201030, 61372045, 61472045, and 61401229), the Science and Technology Project of Jiangsu Province, China (Grant No. BE2015002), the Open Research Program of the State Key Laboratory of Millimeter Waves, China (Grant Nos. K201616 and K201622), and the Nanjing University of Posts and Telecommunications Scientific Foundation, China (Grant No. NY214148).
Haverkort, Maurits W.
2016-05-01
Depending on the material and edge under consideration, core level spectra manifest themselves as local excitons with multiplets, edge singularities, resonances, or the local projected density of states. Both extremes, i.e., local excitons and non-interacting delocalized excitations are theoretically well under control. Describing the intermediate regime, where local many body interactions and band-formation are equally important is a challenge. Here we discuss how Quanty, a versatile quantum many body script language, can be used to calculate a variety of different core level spectroscopy types on solids and molecules, both in the frequency as well as the time domain. The flexible nature of Quanty allows one to choose different approximations for different edges and materials. For example, using a newly developed method merging ideas from density renormalization group and quantum chemistry [1-3], Quanty can calculate excitons, resonances and band-excitations in x-ray absorption, photoemission, x-ray emission, fluorescence yield, non-resonant inelastic x-ray scattering, resonant inelastic x-ray scattering and many more spectroscopy types. Quanty can be obtained from: http://www.quanty.org.
Zahertar, S.; Yalcinkaya, A. D.; Torun, H.
2015-11-01
In this work, transmission characteristics of rectangular split-ring resonators with single-split and two-splits are analyzed at microwave frequencies. The resonators are coupled with monopole antennas for excitation. The scattering parameters of the devices are investigated under different polarizations of E and H fields. The magnetic resonances induced by E and H fields are identified and the differences in the behavior of the resonators due to orientations of the fields are explained based on simulation and experimental results. The addition of the second split of the device is investigated considering different configurations of the excitation vectors. It is demonstrated that the single-split and the two-splits resonators exhibit identical transmission characteristics for a certain excitation configuration as verified with simulations and experiments. The presented resonators can effectively function as frequency selective media for varying excitation conditions.
Directory of Open Access Journals (Sweden)
A. A. Trubin
2010-01-01
Full Text Available It’s proposed the program that is searching the coupling coefficients of dielectric resonators answering to the necessary gain-frequency characteristic of band pass microwave filter. The program is based on a genetic algorithm.
García-Vellisca, M. A.; Pisarchik, A. N.; Jaimes-Reátegui, R.
2016-07-01
We present the experimental evidence of deterministic coherence resonance in unidirectionally coupled two and three Rössler electronic oscillators with mismatch between their natural frequencies. The regularity in both the amplitude and the phase of chaotic fluctuations is experimentally proven by the analyses of normalized standard deviations of the peak amplitude and interpeak interval and Lyapunov exponents. The resonant chaos suppression appears when the coupling strength is increased and the oscillators are in phase synchronization. In two coupled oscillators, the coherence enhancement is associated with negative third and fourth Lyapunov exponents, while the largest first and second exponents remain positive. Distinctly, in three oscillators coupled in a ring, all exponents become negative, giving rise to periodicity. Numerical simulations are in good agreement with the experiments.
Influence of the Basset force on the resonant behavior of an oscillator with fluctuating frequency
Energy Technology Data Exchange (ETDEWEB)
Rekker, A., E-mail: Astrid.Rekker@tlu.ee; Mankin, R., E-mail: Romi.Mankin@tlu.ee [Institute of Mathematics and Natural Sciences, Tallinn University, 29 Narva Road, 10120 Tallinn (Estonia)
2015-10-28
The influence of hydrodynamic interactions, such as Stokes and Basset forces, on the dynamics of a harmonically trapped Brownian tracer is considered. A generalized Langevin equation is used to describe the tracer’s response to an external periodic force and to dichotomous fluctuations of the stiffness of the trapping potential. Relying on the Shapiro-Loginov formula, exact expressions for the complex susceptibility and for the response function are presented. On the basis of these exact formulas, it is demonstrated that interplay of a multiplicative colored noise and the Basset force induced memory effects can generate a variety of cooperation effects, such as multiresonance versus the driving frequency, as well as stochastic resonance versus noise parameters. In particular, in certain parameter regions the response function exhibits a resonance-like enhancement at intermediate values of the intensity of the Basset force. Conditions for the appearance of these effects are also discussed.
Influence of the Basset force on the resonant behavior of an oscillator with fluctuating frequency
Rekker, A.; Mankin, R.
2015-10-01
The influence of hydrodynamic interactions, such as Stokes and Basset forces, on the dynamics of a harmonically trapped Brownian tracer is considered. A generalized Langevin equation is used to describe the tracer's response to an external periodic force and to dichotomous fluctuations of the stiffness of the trapping potential. Relying on the Shapiro-Loginov formula, exact expressions for the complex susceptibility and for the response function are presented. On the basis of these exact formulas, it is demonstrated that interplay of a multiplicative colored noise and the Basset force induced memory effects can generate a variety of cooperation effects, such as multiresonance versus the driving frequency, as well as stochastic resonance versus noise parameters. In particular, in certain parameter regions the response function exhibits a resonance-like enhancement at intermediate values of the intensity of the Basset force. Conditions for the appearance of these effects are also discussed.
A Resonantly-Excited Disk-Oscillation Model of High-Frequency QPOs of Microquasars
Kato, Shoji
2012-01-01
A possible model of twin high-frequency QPOs (HF QPOs) of microquasars is examined. The disk is assumed to have global magnetic fields and to be deformed with a two-armed pattern. In this deformed disk, set of a two-armed ($m=2$) vertical p-mode oscillation and an axisymmetric ($m=0$) g-mode oscillation are considered. They resonantly interact through the disk deformation when their frequencies are the same. This resonant interaction amplifies the set of the above oscillations in the case where these two oscillations have wave energies of opposite signs. These oscillations are assumed to be excited most efficiently in the case where the radial group velocities of these two waves vanish at the same place. The above set of oscillations is not unique, depending on the node number, $n$, of oscillations in the vertical direction. We consider that the basic two sets of oscillations correspond to the twin QPOs. The frequencies of these oscillations depend on disk parameters such as strength of magnetic fields. For o...
Two-dimensional resonance frequency tuning approach for vibration-based energy harvesting
Dong, Lin; Prasad, M. G.; Fisher, Frank T.
2016-06-01
Vibration-based energy harvesting seeks to convert ambient vibrations to electrical energy and is of interest for, among other applications, powering the individual nodes of wireless sensor networks. Generally it is desired to match the resonant frequencies of the device to the ambient vibration source to optimize the energy harvested. This paper presents a two-dimensionally (2D) tunable vibration-based energy harvesting device via the application of magnetic forces in two-dimensional space. These forces are accounted for in the model separately, with the transverse force contributing to the transverse stiffness of the system while the axial force contributes to a change in axial stiffness of the beam. Simulation results from a COMSOL magnetostatic 3D model agree well with the analytical model and are confirmed with a separate experimental study. Furthermore, analysis of the three possible magnetization orientations between the fixed and tuning magnets shows that the transverse parallel magnetization orientation is the most effective with regards to the proposed 2D tuning approach. In all cases the transverse stiffness term is in general significantly larger than the axial stiffness contribution, suggesting that from a tuning perspective it may be possible to use these stiffness contributions for coarse and fine frequency tuning, respectively. This 2D resonant frequency tuning approach extends earlier 1D approaches and may be particularly useful in applications where space constraints impact the available design space of the energy harvester.
A Switched Capacitor Based AC/DC Resonant Converter for High Frequency AC Power Generation
Directory of Open Access Journals (Sweden)
Cuidong Xu
2015-09-01
Full Text Available A switched capacitor based AC-DC resonant power converter is proposed for high frequency power generation output conversion. This converter is suitable for small scale, high frequency wind power generation. It has a high conversion ratio to provide a step down from high voltage to low voltage for easy use. The voltage conversion ratio of conventional switched capacitor power converters is fixed to n, 1/n or −1/n (n is the switched capacitor cell. In this paper, A circuit which can provide n, 1/n and 2n/m of the voltage conversion ratio is presented (n is stepping up the switched capacitor cell, m is stepping down the switching capacitor cell. The conversion ratio can be changed greatly by using only two switches. A resonant tank is used to assist in zero current switching, and hence the current spike, which usually exists in a classical switching switched capacitor converter, can be eliminated. Both easy operation and efficiency are possible. Principles of operation, computer simulations and experimental results of the proposed circuit are presented. General analysis and design methods are given. The experimental result verifies the theoretical analysis of high frequency AC power generation.
Directory of Open Access Journals (Sweden)
Zhen Lin
2015-02-01
Full Text Available The resonator of a solid-state vibratory gyro is responsible for sensing angular motion. Frequency splitting of an axisymmetric-shell resonator is a common problem caused by manufacturing defects. The defect causes a frequency difference between two working modes which consist of two nodes and two antinodes. The difference leads to the loss of gyroscopic effect, and thus the resonator cannot sense angular motion. In this paper, the resonator based on an axisymmetric multi-curved surface shell structure is investigated and an approach to eliminate frequency splits is proposed. Since axisymmetric multi-curved surface shell resonators are too complex to be modeled, this paper proposes a simplified model by focusing on a common property of the axisymmetric shell. The resonator with stochastic imperfections is made equivalent to a perfect shell with an imperfect mass point. Rayleigh’s energy method is used in the theoretical analysis. Finite element modeling is used to demonstrate the effectiveness of the elimination approach. In real cases, a resonator’s frequency split is eliminated by the proposed approach. In this paper, errors in the theoretical analysis are discussed and steps to be taken when the deviation between assumptions and the real situation is large are figured out. The resonator has good performance after processing. The elimination approach can be applied to any kind of solid-state vibratory gyro resonators with an axisymmetric shell structure.
High Frequency Coils for Clinical Nuclear Magnetic Resonance Imaging and Spectroscopy.
Vaughan, John Thomas, Jr.
To extend the inherent signal-to-noise (S/N) advantage of high field (4T+) NMR to clinical imaging and spectroscopy, a new approach to designing RF surface and volume coils is required. As coils approach wavelength dimensions, the performance of conventional lumped element (L,C) designs succumbs to: (1) non uniform current distributions resulting in decreased homogeneity, fill factor, and increased electric field losses, (2) decreased conductor skin depths resulting in increased ohmic losses, and (3) high inductance resulting in self resonance near or below the desired frequency of operation. At lower frequencies the phase change due to finite propagation velocity of transmit and receive signals on coil conductors is negligible. Therefore, the conventional design approach considers a DC (Biot-Savart) field only, for an unloaded (free-space) RF coil. This study recognizes and solves the problems of high field, clinical coil design. At higher radiofrequencies, the distributed nature of the coil and patient structure is considered in both circuit design and theory. Lumped elements are replaced by transmission line and cavity elements. Lumped element circuit theory is replaced by transmission line or transverse electromagnetic (TEM) theory. DC field analysis is replaced with fully time-dependent AC analysis for the coil and the human load. AC field losses and resultant heating in living tissues are investigated with regard to safety assurance for high frequency clinical coil design and application. By designing high frequency coils with the high frequency methods presented herein, desired B1 field characteristics are optimized, coil and patient losses are minimized, and self resonance is maximized. Clinical results obtained with these coils have verified for the first time the clear advantages of human NMR imaging and spectroscopy at 4 Tesla and above.
Vieira, H S
2016-01-01
We study the scattering and the resonant frequencies (quasispectrum) of charged massive scalar waves by Kerr-Newman-Kasuya spacetime (dyon black hole). The equations of motion are written into a Heun form, and its analytical solutions are obtained. We obtain the resonant frequencies expression and the general exact regular partial wave solution. The special cases of the Kerr and Schwarzschild black holes are analyzed and the solutions are shown.
Frequency Shifts of Micro and Nano Cantilever Beam Resonators Due to Added Masses
Bouchaala, Adam M.
2016-03-21
We present analytical and numerical techniques to accurately calculate the shifts in the natural frequencies of electrically actuated micro and nano (carbon nanotubes (CNTs)) cantilever beams implemented as resonant sensors for mass detection of biological entities, particularly Escherichia coli (E. coli) and prostate specific antigen (PSA) cells. The beams are modeled as Euler-Bernoulli beams, including the nonlinear electrostatic forces and the added biological cells, which are modeled as discrete point masses. The frequency shifts due to the added masses of the cells are calculated for the fundamental and higher-order modes of vibrations. Analytical expressions of the natural frequency shifts under a direct current (DC) voltage and an added mass have been developed using perturbation techniques and the Galerkin approximation. Numerical techniques are also used to calculate the frequency shifts and compared with the analytical technique. We found that a hybrid approach that relies on the analytical perturbation expression and the Galerkin procedure for calculating accurately the static behavior presents the most computationally efficient approach. We found that using higher-order modes of vibration of micro-electro-mechanical-system (MEMS) beams or miniaturizing the sizes of the beams to nanoscale leads to significant improved frequency shifts, and thus increased sensitivities. © 2016 by ASME.
ARTgrid: A Two-Level Learning Architecture Based on Adaptive Resonance Theory
Directory of Open Access Journals (Sweden)
Marko Švaco
2014-01-01
Full Text Available This paper proposes a novel neural network architecture based on adaptive resonance theory (ART called ARTgrid that can perform both online and offline clustering of 2D object structures. The main novelty of the proposed architecture is a two-level categorization and search mechanism that can enhance computation speed while maintaining high performance in cases of higher vigilance values. ARTgrid is developed for specific robotic applications for work in unstructured environments with diverse work objects. For that reason simulations are conducted on random generated data which represents actual manipulation objects, that is, their respective 2D structures. ARTgrid verification is done through comparison in clustering speed with the fuzzy ART algorithm and Adaptive Fuzzy Shadow (AFS network. Simulation results show that by applying higher vigilance values (ρ>0.85 clustering performance of ARTgrid is considerably better, while lower vigilance values produce comparable results with the original fuzzy ART algorithm.
Compact infrared continuous-wave double-pass single-frequency doubly-resonant OPO
Boucon, Anne; Bretenaker, Fabien
2014-01-01
We demonstrate a compact continuous-wave single-frequency doubly-resonant optical parametric oscillator (DRO) in a double-pass pump configuration with a control of the relative phase between the reflected waves. The nested DRO cavity allows single longitudinal mode operation together with low threshold and high efficiency. Thermal effects are managed by chopping the pump beam, allowing continuous tuning of the emitted wavelength. The infrared idler wave (3200-3800 nm) can be used for gas detection and the threshold pump power is compatible with diode pumping.
Analysis of Frequency Spectrum of Laser-Induced Vibration of Microbeam Resonators
Institute of Scientific and Technical Information of China (English)
FANG Dai-Ning; SUN Yu-xin; SOH Ai-Kah
2006-01-01
The vibration phenomenon during pulsed laser heating of micro-beams is investigated.The beam is made of silicon and js heated by a laser pulse with a non-Gaussian temporal profile and with an ultrashort pulse duration of 2ps.which incites vibration due to the thermoelastic damping effect.This coupled thermoelastic problem is solved using an analytical-numerical technique based on the Laplace transformation.The damping ratio and resonant frequency shift ratio of beams due t0 the air damping effect and the thermoelastic damping ettect are also examined and discusssed.
Modeling of Nanophotonic Resonators with the Finite-Difference Frequency-Domain Method
DEFF Research Database (Denmark)
Ivinskaya, Aliaksandra; Lavrinenko, Andrei; Shyroki, Dzmitry
2011-01-01
Finite-difference frequency-domain method with perfectly matched layers and free-space squeezing is applied to model open photonic resonators of arbitrary morphology in three dimensions. Treating each spatial dimension independently, nonuniform mesh of continuously varying density can be built...... easily to better resolve mode features. We explore the convergence of the eigenmode wavelength $lambda $ and quality factor $Q$ of an open dielectric sphere and of a very-high- $Q$ photonic crystal cavity calculated with different mesh density distributions. On a grid having, for example, 10 nodes per...
Wavelength-sized GaAs optomechanical resonators with GHz frequency
Ding, Lu; Senellart, Pascale; Lemaitre, Aristide; Ducci, Sara; Leo, Giuseppe; Favero, Ivan
2011-01-01
We report on wavelength-sized GaAs optomechanical disk resonators showing ultra-strong optomechanical interaction. We observe optical transduction of a disk mechanical breathing mode with 1.4 GHz frequency and effective mass of ~ 2 pg. The measured vacuum optomechanical coupling rate reaches 0.8 MHz, with a related differential optomechanical coupling factor of 485 GHz/nm. The disk Brownian motion is optically resolved with a sensitivity of 10-17 m/{\\sqrt}Hz at room temperature and pressure.
Köcher, S S; Heydenreich, T; Glaser, S J
2014-10-17
We study the utility of joint time-frequency representations for the analysis of shaped or composite pulses for magnetic resonance. Such spectrograms are commonly used for the visualization of shaped laser pulses in optical spectroscopy. This intuitive representation provides additional insight compared to conventional approaches, which exclusively show either temporal or spectral information. We focus on the short-time Fourier transform, which provides not only amplitude but also phase information. The approach is illustrated for broadband inversion pulses, multiple quantum excitation and broadband heteronuclear decoupling. The physical interpretation and validity of the approach is discussed.
EVENT-DRIVEN SIMULATION OF INTEGRATE-AND-FIRE MODELS WITH SPIKE-FREQUENCY ADAPTATION
Institute of Scientific and Technical Information of China (English)
Lin Xianghong; Zhang Tianwen
2009-01-01
The evoked spike discharges of a neuron depend critically on the recent history of its electrical activity. A well-known example is the phenomenon of spike-frequency adaptation that is a commonly observed property of neurons. In this paper, using a leaky integrate-and-fire model that includes an adaptation current, we propose an event-driven strategy to simulate integrate-and-fire models with spike-frequency adaptation. Such approach is more precise than traditional clock-driven numerical integration approach because the timing of spikes is treated exactly. In experiments, using event-driven and clock-driven strategies we simulated the adaptation time course of single neuron and the random network with spike-timing dependent plasticity, the results indicate that (1) the temporal precision of spiking events impacts on neuronal dynamics of single as well as network in the different simulation strategies and (2) the simulation time scales linearly with the total number of spiking events in the event-driven simulation strategies.
Electrogravitational Resonance of a Gaussian Beam to a High-Frequency Relic Gravitational Wave
Institute of Scientific and Technical Information of China (English)
李芳昱; 唐孟希
2001-01-01
We consider the resonant response of a Gaussian beam passing through a static magnetic field to a high-frequency relic gravitational wave (GW). It is found that under the synchroresonance condition, the first-order perturbative electromagnetic energy fluxes will contain a "left circular wave" and a "right circular wave" around the symmetrical axis of the Gaussian beam, but the perturbative effects produced by the + and × polarization of the GW have a different physical behaviour. For the high-frequency relic GW with vg = 1010 Hz, h = l0-30, recently expected by the quintessential inflationary models, the corresponding perturbative photon flux passing through the region 10-2 m2 would be expected to be 104 s-1. This is the largest perturbative photon flux we have recently analysed and estimated using the typical laboratory parameters.
High-frequency performance of electric field sensors aboard the RESONANCE satellite
Sampl, M.; Macher, W.; Gruber, C.; Oswald, T.; Kapper, M.; Rucker, H. O.; Mogilevsky, M.
2015-05-01
We present the high-frequency properties of the eight electric field sensors as proposed to be launched on the spacecraft "RESONANCE" in the near future. Due to the close proximity of the conducting spacecraft body, the sensors (antennas) have complex receiving features and need to be well understood for an optimal mission and spacecraft design. An optimal configuration and precise understanding of the sensor and antenna characteristics is also vital for the proper performance of spaceborne scientific instrumentation and the corresponding data analysis. The provided results are particularly interesting with regard to the planned mutual impedance experiment for measuring plasma parameters. Our computational results describe the extreme dependency of the sensor system with regard to wave incident direction and frequency, and provides the full description of the sensor system as a multi-port scatterer. In particular, goniopolarimetry techniques like polarization analysis and direction finding depend crucially on the presented antenna characteristics.
DEFF Research Database (Denmark)
Liang, Shanshan; Crovetto, Andrea; Peng, Zhuoteng;
2016-01-01
This paper reports on a bi-resonant structure of piezoelectric PVDF films energy harvester (PPEH), which consists of two cantilevers with resonant frequencies of 15 Hz and 22 Hz. With increased acceleration, the vibration amplitudes of the two cantilever-mass structures are increased and collision...... and experiments with piezoelectric elements show that the energy harvesting device with the bi-resonant structure can generate higher power output than that of the sum of the two separate devices from random vibration sources at low frequency, and hence significantly improves the vibration-to- electricity...
Planar Lithographed Superconducting LC Resonators for Frequency-Domain Multiplexed Readout Systems
Rotermund, K.; Barch, B.; Chapman, S.; Hattori, K.; Lee, A.; Palaio, N.; Shirley, I.; Suzuki, A.; Tran, C.
2016-07-01
Cosmic microwave background (CMB) polarization experiments are increasing the number of transition edge sensor (TES) bolometers to increase sensitivity. In order to maintain low thermal loading of the sub-Kelvin stage, the frequency-domain multiplexing (FDM) factor has to increase accordingly. FDM is achieved by placing TES bolometers in series with inductor-capacitor (LC) resonators, which select the readout frequency. The multiplexing factor can be raised with a large total readout bandwidth and small frequency spacing between channels. The inductance is kept constant to maintain a uniform readout bandwidth across detectors, while the maximum acceptable value is determined by bolometer stability. Current technology relies on commercially available ceramic chip capacitors. These have high scatter in their capacitance thereby requiring large frequency spacing. Furthermore, they have high equivalent series resistance (ESR) at higher frequencies and are time consuming and tedious to hand assemble via soldering. A solution lies in lithographed, planar spiral inductors (currently in use by some experiments) combined with interdigitated capacitors on a silicon (Si) substrate. To maintain reasonable device dimensions, we have reduced trace and gap widths of the LCs to 4 \\upmu m. We increased the inductance from 16 to 60 \\upmu H to achieve a higher packing density, a requirement for FDM systems with large multiplexing factors. Additionally, the Si substrate yields low ESR values across the entire frequency range and lithography makes mass production of LC pairs possible. We reduced mutual inductance between inductors by placing them in a checkerboard pattern with the capacitors, thereby increasing physical distances between adjacent inductors. We also reduce magnetic coupling of inductors with external sources by evaporating a superconducting ground plane onto the backside of the substrate. We report on the development of lithographed LCs in the 1-5 MHz range for use
Directory of Open Access Journals (Sweden)
Mohamed Sultan Mohamed Ali
2014-07-01
Full Text Available This paper reports a method that enables real-time displacement monitoring and control of micromachined resonant-type actuators using wireless radiofrequency (RF. The method is applied to an out-of-plane, spiral-coil microactuator based on shape-memory-alloy (SMA. The SMA spiral coil forms an inductor-capacitor resonant circuit that is excited using external RF magnetic fields to thermally actuate the coil. The actuation causes a shift in the circuit’s resonance as the coil is displaced vertically, which is wirelessly monitored through an external antenna to track the displacements. Controlled actuation and displacement monitoring using the developed method is demonstrated with the microfabricated device. The device exhibits a frequency sensitivity to displacement of 10 kHz/µm or more for a full out-of-plane travel range of 466 µm and an average actuation velocity of up to 155 µm/s. The method described permits the actuator to have a self-sensing function that is passively operated, thereby eliminating the need for separate sensors and batteries on the device, thus realizing precise control while attaining a high level of miniaturization in the device.
Conchouso, David; McKerricher, Garret; Arevalo, Arpys; Castro, David; Shamim, Atif; Foulds, Ian G
2016-08-16
Scaled-up production of microfluidic droplets, through the parallelization of hundreds of droplet generators, has received a lot of attention to bring novel multiphase microfluidics research to industrial applications. However, apart from droplet generation, other significant challenges relevant to this goal have never been discussed. Examples include monitoring systems, high-throughput processing of droplets and quality control procedures among others. In this paper, we present and compare capacitive and radio frequency (RF) resonator sensors as two candidates that can measure the dielectric properties of emulsions in microfluidic channels. By placing several of these sensors in a parallelization device, the stability of the droplet generation at different locations can be compared, and potential malfunctions can be detected. This strategy enables for the first time the monitoring of scaled-up microfluidic droplet production. Both sensors were prototyped and characterized using emulsions with droplets of 100-150 μm in diameter, which were generated in parallelization devices at water-in-oil volume fractions (φ) between 11.1% and 33.3%.Using these sensors, we were able to measure accurately increments as small as 2.4% in the water volume fraction of the emulsions. Although both methods rely on the dielectric properties of the emulsions, the main advantage of the RF resonator sensors is the fact that they can be designed to resonate at multiple frequencies of the broadband transmission line. Consequently with careful design, two or more sensors can be parallelized and read out by a single signal. Finally, a comparison between these sensors based on their sensitivity, readout cost and simplicity, and design flexibility is also discussed.
International Nuclear Information System (INIS)
The total components of the accelerator are the magnetron, electron gun, accelerating structure, a set of solenoid magnets, four sets of steering coils, a modulator, and a circulator. One of the accelerator components of the accelerating structure is made of oxygen-free high-conductivity copper (OFHC), and its volume is changed according to the ambient temperature. As the volume changes, the resonant frequency of the accelerating structure is changed. Accordingly, the resonance frequency is mismatched between the source of the magnetron and the accelerating structure. An automatic frequency tuning system is automatically matched with the resonant frequency of the magnetron and accelerating structure, which allows a high output power and reliable accelerator operation. An automatic frequency tuning system is composed of a step motor control part for correcting the frequency of the source and power measuring parts, i.e., the forward and reflected power between the magnetron and accelerating structure. In this paper, the design, fabrication, and RF power test of the automatic frequency tuning system for the X-band linac are presented. A frequency tuning system was developed to overcome an unstable accelerator operation owing to the frequency mismatch between the magnetron and accelerating structure. The frequency measurement accuracy is 100 kHz and 0.72 degree per pulse
Energy Technology Data Exchange (ETDEWEB)
Cha, Sung Su; Lee, Byung Cheol [University of Science and Technology, Daejeon (Korea, Republic of); Kim, Yujong; Park, Hyung Dal; Lee, Byeong-No; Joo, Youngwoo; Cha, Hyungki; Lee, Soo Min; Song, Ki Baek [KAERI, Daejeon (Korea, Republic of); Lee, Seung Hyun [Sungkyunkwan University, Suwon (Korea, Republic of)
2015-05-15
The total components of the accelerator are the magnetron, electron gun, accelerating structure, a set of solenoid magnets, four sets of steering coils, a modulator, and a circulator. One of the accelerator components of the accelerating structure is made of oxygen-free high-conductivity copper (OFHC), and its volume is changed according to the ambient temperature. As the volume changes, the resonant frequency of the accelerating structure is changed. Accordingly, the resonance frequency is mismatched between the source of the magnetron and the accelerating structure. An automatic frequency tuning system is automatically matched with the resonant frequency of the magnetron and accelerating structure, which allows a high output power and reliable accelerator operation. An automatic frequency tuning system is composed of a step motor control part for correcting the frequency of the source and power measuring parts, i.e., the forward and reflected power between the magnetron and accelerating structure. In this paper, the design, fabrication, and RF power test of the automatic frequency tuning system for the X-band linac are presented. A frequency tuning system was developed to overcome an unstable accelerator operation owing to the frequency mismatch between the magnetron and accelerating structure. The frequency measurement accuracy is 100 kHz and 0.72 degree per pulse.
Generation of constant-amplitude radio-frequency sweeps at a tunnel junction for spin resonance STM
Paul, William; Baumann, Susanne; Lutz, Christopher P.; Heinrich, Andreas J.
2016-07-01
We describe the measurement and successful compensation of the radio-frequency transfer function of a scanning tunneling microscope over a wide frequency range (15.5-35.5 GHz) and with high dynamic range (>50 dB). The precise compensation of cabling resonances and attenuations is critical for the production of constant-voltage frequency sweeps for electric-field driven electron spin resonance (ESR) experiments. We also demonstrate that a well-calibrated tunnel junction voltage is necessary to avoid spurious ESR peaks that can arise due to a non-flat transfer function.
Kristiansen, Ulf R; Pinhède, Cédric; Amielh, Muriel
2010-01-01
It is well known that an air flow in a corrugated pipe might excite the longitudinal acoustic modes of the pipe. In this letter is reported experiments where a low frequency, oscillating flow with velocity magnitudes of the same order as the air flow has been added. Depending on the oscillation strength, it might silence the pipe or move the resonances to higher harmonics. It is also shown that a low frequency oscillation by itself might excite a higher frequency acoustic resonance of the pipe.
Breger, Michel (Hrsg.); Montgomery, Michael H.
2014-01-01
In the theory of resonant mode coupling, the parent and child modes are directly related in frequency and phase. The oscillations present in the fast rotating Delta Scuti star KIC 8054146 allow us to test the most general and generic aspects of such a theory. The only direct way to separate the parent and coupled (child) modes is to examine the correlations in amplitude variability between the different frequencies. For the dominant family of related frequencies, only a single mode and a trip...
Ultra-high frequency, high Q/volume micromechanical resonators in a planar AlN phononic crystal
Ghasemi Baboly, M.; Alaie, S.; Reinke, C. M.; El-Kady, I.; Leseman, Z. C.
2016-07-01
This paper presents the first design and experimental demonstration of an ultrahigh frequency complete phononic crystal (PnC) bandgap aluminum nitride (AlN)/air structure operating in the GHz range. A complete phononic bandgap of this design is used to efficiently and simultaneously confine elastic vibrations in a resonator. The PnC structure is fabricated by etching a square array of air holes in an AlN slab. The fabricated PnC resonator resonates at 1.117 GHz, which corresponds to an out-of-plane mode. The measured bandgap and resonance frequencies are in very good agreement with the eigen-frequency and frequency-domain finite element analyses. As a result, a quality factor/volume of 7.6 × 1017/m3 for the confined resonance mode was obtained that is the largest value reported for this type of PnC resonator to date. These results are an important step forward in achieving possible applications of PnCs for RF communication and signal processing with smaller dimensions.
Directory of Open Access Journals (Sweden)
Seunghyun Eom
2016-10-01
Full Text Available In this paper, we proposed a stretchable radio frequency (RF sensor to detect strain direction and level. The stretchable sensor is composed of two complementary split ring resonators (CSRR with microfluidic channels. In order to achieve stretchability, liquid metal (eutectic gallium-indium, EGaIn and Ecoflex substrate are used. Microfluidic channels are built by Ecoflex elastomer and microfluidic channel frames. A three-dimensional (3D printer is used for fabrication of microfluidic channel frames. Two CSRR resonators are designed to resonate 2.03 GHz and 3.68 GHz. When the proposed sensor is stretched from 0 to 8 mm along the +x direction, the resonant frequency is shifted from 3.68 GHz to 3.13 GHz. When the proposed sensor is stretched from 0 to 8 mm along the −x direction, the resonant frequency is shifted from 2.03 GHz to 1.78 GHz. Therefore, we can detect stretched length and direction from independent variation of two resonant frequencies.
Directory of Open Access Journals (Sweden)
M. N.Osman
2015-04-01
Full Text Available In this paper, an electronically polarization reconfigurable circular patch antenna with fixed resonant frequency operating at Wireless Local Area Network (WLAN frequency band (2.4-2.48 GHz is presented. The structure of the proposed design consists of a circular patch as a radiating element fed by coaxial probe, cooperated with four equal-length slits etched on the edge along x-axis and y-axis. A total of four switches was used and embedded across the slits at specific locations, thus controlled the length of the slits. By activating and deactivating the switches (ON and OFF across the slits, the current on the patch is changed, thus modifying the electric field and polarization of the antenna. Consequently, the polarization excited by the proposed antenna can be switched into three types, either linear polarization, left-hand circular polarization or right-hand circular polarization. This paper proposes a simple approach that able to switch the polarizations and excited at the same operating frequency. Simulated and measured results of ideal case (using copper strip switches and real case (using PIN diode switches are compared and presented to demonstrate the performance of the antenna.
Spin torque resonant vortex core expulsion for an efficient radio-frequency detection scheme
Cros, V.; Jenkins, A. S.; Lebrun, R.; Bortolotti, P.; Grimaldi, E.; Tsunegi, S.; Kubota, H.; Yakushiji, K.; Fukushima, A.; Yuasa, S.
It has been proposed by Tulaparkur et al.[1ref] that a high frequency detector based on the so called spin-diode effect in spin transfer oscillators could eventually replace conventional Schottky diodes, due to their nanoscale size, frequency tunability, and large output sensitivity. Although a promising candidate for ICT applications, the output voltage generated from this effect is consistently low. Here we present a scheme for a new type of spintronics-based high frequency detector based on the expulsion of the vortex core of a magnetic tunnel junction. The resonant expulsion of the core leads to a large and sharp change in resistance associated with the difference in magnetoresistance between the vortex ground state and the final C-state, which is predominantly in either the parallel or anti-parallel direction relative to the polariser layer. Interestingly, this reversible effect is independent of the incoming rf current amplitude, offering a compelling perspective for a fast real-time rf threshold detector. REF : EU FP7 Grant (MOSAIC No. ICT-FP7-317950 is acknowledged.
Energy Technology Data Exchange (ETDEWEB)
McGee, K P; Lake, D; Mariappan, Y; Manduca, A; Ehman, R L [Department of Radiology, Mayo Clinic College of Medicine, 200 First Street, SW, Rochester, MN 55905 (United States); Hubmayr, R D [Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Mayo Clinic College of Medicine, 200 First Street, SW, Rochester, MN 55905 (United States); Ansell, K, E-mail: mcgee.kiaran@mayo.edu [Schaeffer Academy, 2700 Schaeffer Lane NE, Rochester, MN 55906 (United States)
2011-07-21
Magnetic resonance elastography (MRE) is a non-invasive phase-contrast-based method for quantifying the shear stiffness of biological tissues. Synchronous application of a shear wave source and motion encoding gradient waveforms within the MRE pulse sequence enable visualization of the propagating shear wave throughout the medium under investigation. Encoded shear wave-induced displacements are then processed to calculate the local shear stiffness of each voxel. An important consideration in local shear stiffness estimates is that the algorithms employed typically calculate shear stiffness using relatively high signal-to-noise ratio (SNR) MRE images and have difficulties at an extremely low SNR. A new method of estimating shear stiffness based on the principal spatial frequency of the shear wave displacement map is presented. Finite element simulations were performed to assess the relative insensitivity of this approach to decreases in SNR. Additionally, ex vivo experiments were conducted on normal rat lungs to assess the robustness of this approach in low SNR biological tissue. Simulation and experimental results indicate that calculation of shear stiffness by the principal frequency method is less sensitive to extremely low SNR than previously reported MRE inversion methods but at the expense of loss of spatial information within the region of interest from which the principal frequency estimate is derived.
Zhang, Yongbo; Wang, Peng; Ma, Tianyong; Wang, Ying; Qiao, Liang; Wang, Tao
2016-02-01
Planar anisotropy Nd2Co17 flakes fractured along c crystal plane were fabricated by surfactant-assisted high-energy ball milling technique. The magnetic flakes have a diameter range of 5-20 μm and a typical thickness of approximately 120 nm. The frequency dependence of complex permeability of Nd2Co17 epoxy resin composite has been investigated in the frequency range of 0.1-18 GHz. The measurement results show that the natural resonance frequency reaches 12.5 GHz while the initial permeability survives up to 2.26. The superior high frequency properties come from the large out-of-plane anisotropy field and the flake structure fractured along the c crystal plane of Nd2Co17. The planar anisotropic Nd2Co17 flakes have significant potential applications in the high-frequency devices working in the frequency beyond 10 GHz.
A New Adaptive Channel Estimation for Frequency Selective Time Varying Fading OFDM Channels
Afifi, Wessam M
2010-01-01
In this paper a new algorithm for adaptive dynamic channel estimation for frequency selective time varying fading OFDM channels is proposed. The new algorithm adopts a new strategy that successfully increases OFDM symbol rate. Instead of using a fixed training pilot sequence, the proposed algorithm uses a logic controller to choose among several available training patterns. The controller choice is based on the cross-correlation between pilot symbols over two consecutive time instants (which is considered to be a suitable measure of channel stationarity) as well as the deviation from the desired BER. Simulation results of the system performance confirm the effectiveness of this new channel estimation technique over traditional non-adaptive estimation methods in increasing the data rate of OFDM symbols while maintaining the same probability of error.
Directory of Open Access Journals (Sweden)
Daniel Mietchen
Full Text Available BACKGROUND: Temperatures below the freezing point of water and the ensuing ice crystal formation pose serious challenges to cell structure and function. Consequently, species living in seasonally cold environments have evolved a multitude of strategies to reorganize their cellular architecture and metabolism, and the underlying mechanisms are crucial to our understanding of life. In multicellular organisms, and poikilotherm animals in particular, our knowledge about these processes is almost exclusively due to invasive studies, thereby limiting the range of conclusions that can be drawn about intact living systems. METHODOLOGY: Given that non-destructive techniques like (1H Magnetic Resonance (MR imaging and spectroscopy have proven useful for in vivo investigations of a wide range of biological systems, we aimed at evaluating their potential to observe cold adaptations in living insect larvae. Specifically, we chose two cold-hardy insect species that frequently serve as cryobiological model systems--the freeze-avoiding gall moth Epiblema scudderiana and the freeze-tolerant gall fly Eurosta solidaginis. RESULTS: In vivo MR images were acquired from autumn-collected larvae at temperatures between 0 degrees C and about -70 degrees C and at spatial resolutions down to 27 microm. These images revealed three-dimensional (3D larval anatomy at a level of detail currently not in reach of other in vivo techniques. Furthermore, they allowed visualization of the 3D distribution of the remaining liquid water and of the endogenous cryoprotectants at subzero temperatures, and temperature-weighted images of these distributions could be derived. Finally, individual fat body cells and their nuclei could be identified in intact frozen Eurosta larvae. CONCLUSIONS: These findings suggest that high resolution MR techniques provide for interesting methodological options in comparative cryobiological investigations, especially in vivo.
A single coil radio frequency gradient probe for nuclear magnetic resonance applications.
Christofield, N; Sobieski, D N; Erker, J C; May, S; Augustine, M P
2012-12-01
A single coil nuclear magnetic resonance (NMR) probehead and associated electronics capable of asynchronously applying both homogeneous and inhomogeneous radio frequency (rf) pulses to solid, liquid, or gaseous samples is described. This equipment can be interfaced with a conventional single channel NMR spectrometer. Carefully placed PIN diodes on the NMR probehead are used to switch the coil between a homogeneous end tapped configuration and an inhomogeneous center tapped rf gradient configuration. This approach dramatically improves channel isolation in comparison to existing two coil designs. Descriptions of the new probehead, the transistor-transistor logic (TTL) controlled dc pulser for PIN diode gating, and the high power rf switch are provided. Several NMR pulse sequences are used to test the channel isolation and probe performance. Finally an application to liquid phase solvent suppression is provided. PMID:23278008
Hirth, Michael; Kuhn, Jochen; Müller, Andreas
2015-02-01
Recent articles about smartphone experiments have described their applications as experimental tools in different physical contexts.1-4 They have established that smartphones facilitate experimental setups, thanks to the small size and diverse functions of mobile devices, in comparison to setups with computer-based measurements. In the experiment described in this article, the experimental setup is reduced to a minimum. The objective of the experiment is to determine the speed of sound with a high degree of accuracy using everyday tools. An article published recently proposes a time-of-flight method where sound or acoustic pulses are reflected at the ends of an open tube.5 In contrast, the following experiment idea is based on the harmonic resonant frequencies of such a tube, simultaneously triggered by a noise signal.
Electromagnetic Response of High-Frequency Gravitational Waves by Coupling Open Resonant Cavity
Institute of Scientific and Technical Information of China (English)
LI Fang-Yu; CHEN Ying; WANG Ping
2007-01-01
We present a new detecting scheme of high-frequency gravitational waves(HFGWs) in the GHz band,the scheme consists of a high-quality-factor open microwave cavity,a static magnetic field passing through the cavity and an electromagnetic (EM)normal mode stored in the cavity.It is found that under the resonant condition firstand second-order perturbation EM effects have almost the same detecting sensitivity to the HFGWs in the GHz band (h～10-26,v～5GHz),but the former contains more information from the HFGWs.We akso provide a very brief review for possible improving way of the sensitivity.This scheme would be Highly complementary to other schemes of detecting the HFGWs.
Energy Technology Data Exchange (ETDEWEB)
Duden, Thomas; Radmilovic, Velimir
2009-03-04
We describe a setup for the resonance frequency measurement of individual microcantilevers. The setup displays both high spatial selectivity and sensitivity to specimen vibrations by utilizing a tapered uncoated fiber tip. The high sensitivity to specimen vibrations is achieved by the combination of optical Fabry-Perot interferometry and narrow band RF detection. Wave fronts reflected on the specimen and on the fiber tip end face interfere, thus no reference plane on the specimen is needed, as demonstrated with the example of freestanding silicon nitride micro-cantilevers. The resulting system is integrated in a DB-235 dual beam FIB system, thereby allowing the measurement of micro-cantilever responses during observation in SEM mode. The FIB was used to modify the optical fiber tip. At this point of our RF system development, the microcantilevers used to characterize the detector were not modified in situ.
High frequency electro-optic measurement of strained silicon racetrack resonators
Borghi, Massimo; Mancinelli, Mattia; Merget, Florian; Witzens, Jeremy; Bernard, Martino; Ghulinyan, Mher; Pucker, Georg; Pavesi, Lorenzo
2016-05-01
In this paper, we report on time resolved electro-optic measurements in strained silicon resonators. Strain is induced by applying a mechanical deformation to the device. It is demonstrated that the linear electro-optic effect vanishes when the applied voltage modulation varies much faster than the free carrier lifetime, and that this occurs independently on the level of the applied stress. This demonstrates that, at frequencies which lie below the free carrier recombination rate, the electro-optic modulation is caused by plasma carrier dispersion. After normalizing out free carrier effects, it is found an upper limit of (8 +/- 3) pm/V to the value of the strain induced χ(2)eff, zzz tensor component. This is an order of magnitude lower than the previously reported values for static electro-optic measurements.
Designing shielded radio-frequency phased-array coils for magnetic resonance imaging
Institute of Scientific and Technical Information of China (English)
Xu Wen-Long; Zhang Ju-Cheng; Li Xia; Xu Bing-Qiao; Tao Gui-Sheng
2013-01-01
In this paper,an approach to the design of shielded radio-frequency (RF) phased-array coils for magnetic resonance imaging (MRI) is proposed.The target field method is used to find current densities distributed on primary and shield coils.The stream function technique is used to discretize current densities and to obtain the winding patterns of the coils.The corresponding highly ill-conditioned integral equation is solved by the Tikhonov regularization with a penalty function related to the minimum curvature.To balance the simplicity and smoothness with the homogeneity of the magnetic field of the coil's winding pattern,the selection of a penalty factor is discussed in detail.
Use of a radio-frequency resonance circuit in studies of alkali ionization in flames
International Nuclear Information System (INIS)
The context of the investigations are outlined with a short review about recent flame studies at Utrecht University and a discussion about discrepancies and agreements in the literature concerning alkali ionization in flames. The measuring technique chosen is described and the general design of the radio-frequency resonance system presented. The optical track measurements and the theoretical calculations of flame rise velocity are dealt with. The collisional ionization rate constants for Na, K and Cs are determined. The collisional-ionization rate constant for lithium is treated separately by reason of the hydroxide formation. Finally a theoretical model for the conducting flame in a weak, alternating electric field is developed. The relation betaeen the admittance and the flame conductivity in first order approximations is derived. (Auth.)
Simple analytical expression for the peak-frequency shifts of plasmonic resonances for sensing
Yang, Jianji; Lalanne, Philippe
2015-01-01
We derive a closed-form expression that accurately predicts the peak frequency-shift and broadening induced by tiny perturbations of plasmonic nanoresonators without critically relying on repeated electrodynamic simulations of the spectral response of nanoresonator for various locations, sizes or shapes of the perturbing objects. The force of the present approach, in comparison with other approaches of the same kind, is that the derivation is supported by a mathematical formalism based on a rigorous normalization of the resonance modes of nanoresonators consisting of lossy and dispersive materials. Accordingly, accurate predictions are obtained for a large range of nanoparticle shapes and sizes, used in various plasmonic nanosensors, even beyond the quasistatic limit. The expression gives quantitative insight, and combined with an open-source code, provides accurate and fast predictions that are ideally suited for preliminary designs or for interpretation of experimental data. It is also valid for photonic re...
Optical sum-frequency generation in a whispering-gallery-mode resonator
International Nuclear Information System (INIS)
We demonstrate sum-frequency generation between a telecom wavelength and the Rb D2 line, achieved through natural phase matching in a nonlinear whispering gallery mode resonator. Due to the strong optical field confinement and ultra high Q of the cavity, the process saturates already at sub-mW pump peak power, at least two orders of magnitude lower than in existing waveguide-based devices. The experimental data are in agreement with the nonlinear dynamics and phase matching theory based on spherical geometry. Our experimental and theoretical results point toward a new platform for manipulating the color and quantum states of light waves for applications such as atomic memory based quantum networking and logic operations with optical signals. (paper)
Tuning the resonant frequencies of a drop by a magnetic field
Jamin, Timothée; Djama, Yacine; Bacri, Jean-Claude; Falcon, Eric
2016-06-01
We report an experimental study of a magnetic liquid drop deposited on a superhydrophobic substrate and subjected to vertical vibrations in the presence of a static magnetic field. It is well known that a flattened drop of usual liquid displays oscillating lobes at its periphery when vibrated. By adding ferromagnetic nanoparticles to a water drop and varying the strength of the magnetic field, we are experimentally able to efficiently tune the resonant frequencies of the drop. By using conservation energy arguments, we show that the magnetic field contribution is equivalent to adding an effective negative surface tension to the drop. Our model is found to be in good agreement with the experiments with no fitting parameter.
Tuning the resonant frequencies of a drop by a magnetic field
Jamin, Timothée; Bacri, Jean-Claude; Falcon, Eric
2016-01-01
We report an experimental study of a magnetic liquid drop deposited on a superhydrophobic substrate and subjected to vertical vibrations in presence of a static magnetic field. It is well-known that a flattened drop of usual liquid displays oscillating lobes at its periphery when vibrated. By adding ferromagnetic nanoparticles to a water drop and varying the strength of the magnetic field, we are experimentally able to efficiently tune the resonant frequencies of the drop. By using conservation energy arguments, we show that the magnetic field contribution is equivalent to adding an effective negative surface tension to the drop. Our model is found in good agreement with the experiments with no fitting parameter.
Nair, T R Gopalakrishnan
2012-01-01
One of the major challenges of cloud computing is the management of request-response coupling and optimal allocation strategies of computational resources for the various types of service requests. In the normal situations the intelligence required to classify the nature and order of the request using standard methods is insufficient because the arrival of request is at a random fashion and it is meant for multiple resources with different priority order and variety. Hence, it becomes absolutely essential that we identify the trends of different request streams in every category by auto classifications and organize preallocation strategies in a predictive way. It calls for designs of intelligent modes of interaction between the client request and cloud computing resource manager. This paper discusses about the corresponding scheme using Adaptive Resonance Theory-2.
An Adaptive Steganographic Method in Frequency Domain Based on Statistical Metrics of Image
Directory of Open Access Journals (Sweden)
Seyyed Amin Seyyedi
2015-05-01
Full Text Available Steganography is a branch of information hiding. A tradeoff between the hiding payload and quality of digital image steganographic schemes is major challenge of the steganographic methods. An adaptive steganographic method for embedding secret message into gray scale images is proposed. Before embedding the secret message, the cover image is transformed into frequency domain by integer wavelet. The middle frequency band of cover image is partitioned into 4×4 non overlapping blocks. The blocks by deviation and entropy metrics are classified into three categories: smooth, edge, and texture regions. Number of bits which can be embedded in a block is defined by block features. Moreover, RC4 encryption method is used to increase secrecy protection. Experimental results denote the feasibility of the proposed method. Statistical tests were conducted to collect related data to verify the security of method.
Ito, Shinji; Hyodo, Fuminori
2016-02-01
Highly water-soluble ubiquinone-0 (CoQ0) reacts with ascorbate monoanion (Asc) to mediate the production of ascorbyl free radicals (AFR). Using aqueous reaction mixture of CoQ0 and Asc, we obtained positively enhanced dynamic nuclear polarization (DNP)-magnetic resonance (MR) images of the AFR at low frequency (ranging from 515 to 530 MHz) of electron spin resonance (ESR) irradiation. The shape of the determined DNP spectrum was similar to ESR absorption spectra with doublet spectral peaks. The relative locational relationship of spectral peaks in the DNP spectra between the AFR (520 and 525 MHz), 14N-labeled carbamoyl-PROXYL (14N-CmP) (526.5 MHz), and Oxo63 (522 MHz) was different from that in the X-band ESR spectra, but were similar to that in the 300-MHz ESR spectra. The ratio of DNP enhancement to radical concentration for the AFR was higher than those for 14N-CmP, Oxo63, and flavin semiquinone radicals. The spectroscopic DNP properties observed for the AFR were essentially the same as those for AFR mediated by pyrroloquinoline quinone. Moreover, we made a success of in vivo DNP-MR imaging of the CoQ0-mediated AFR which was administered by the subcutaneous and oral injections as an imaging probe.
Fried, Jasper P.; Metaxas, Peter J.
2016-02-01
We have carried out micromagnetic simulations of the gyrotropic resonance mode of a magnetic vortex in the presence of spatially localized and spatially uniform out-of-plane magnetic fields. We show that the field-induced change in the gyrotropic mode frequency is significantly larger when the field is centrally localized over lengths which are comparable to or a few times larger than the vortex core radius. When aligned with the core magnetization, such fields generate an additional confinement of the core. This confinement increases the vortex stiffness in the small-displacement limit, leading to a resonance shift which is greater than that expected for a uniform out-of-plane field of the same amplitude. Fields generated by uniformly magnetized spherical particles having a fixed separation from the disk are found to generate analogous effects except that there is a maximum in the shift at intermediate particle sizes where field localization and stray field magnitude combine optimally to generate a maximum confinement.
Schulze, A; Schaller, P; Dinger, J; Winkler, U; Gmyrek, D
1990-12-01
Ten anesthetized, tracheotomized, adult rabbits were used to test the validity of a method for calculation of total respiratory system compliance from resonant frequency (Cr). Reference values were obtained during constant flow inflation of the relaxed respiratory system by dividing the volume gain by the related difference in pressure at the airway opening (inflation method compliance, Ci). The animals were connected to a new type of servo-controlled infant ventilator. Besides volume-controlled mechanical ventilation at constant inspiratory flow rate and intermittent mandatory ventilation, there is a negative ventilator resistance mode integrated in this device for resistive unloading (Schulze A, Schaller P, Gehrhardt B, Mädler H-J, Gmyrek D: Pediatr Res 28:79-82, 1990). To measure resonant frequency (fr), the respiratory system was totally unloaded for a short period by a negative ventilator resistance exceeding the combined resistances of the endotracheal tube and airways. This evoked a continuous oscillation at fr. By analogy with electrical circuit theory, Cr was calculated according to C = 1/(4 pi 2.I.fr2) where C is compliance and I is inertance. The inertance of the endotracheal tube is given and that of the bronchial tree was ignored assuming a much greater total cross-sectional area and therefore much lower inertance when compared with the endotracheal tube. Three pairs of Ci - Cr values were obtained from each animal: 1) during intact respiratory muscle activity; 2) after pancuronium relaxation, and 3) after surfactant depletion by saline washout.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2284157
Zheng, Bin; Tublin, Mitchell E.; Lederman, Dror; Klym, Amy H.; Brown, Erica D.; Gur, David
2012-02-01
The incidence of thyroid cancer is rising faster than other malignancies and has nearly doubled in the United States (U.S.) in the last 30 years. However, classifying between malignant and benign thyroid nodules is often difficult. Although ultrasound guided Fine Needle Aspiration Biopsy (FNAB) is considered an excellent tool for triaging patients, up to 25% of FNABs are inconclusive. As a result, definitive diagnosis requires an exploratory surgery and a large number of these are performed in the U.S. annually. It would be extremely beneficial to develop a non-invasive tool or procedure that could assist in assessing the likelihood of malignancy of otherwise indeterminate thyroid nodules, thereby reducing the number of exploratory thyroidectomies that are performed under general anesthesia. In this preliminary study we demonstrate a unique hand-held Resonance-frequency based Electrical Impedance Spectroscopy (REIS) device with six pairs of detection probes to detect and classify thyroid nodules using multi-channel EIS output signal sweeps. Under an Institutional Review Board (IRB)-approved case collection protocol, this REIS device is being tested in our clinical facility and we have been collecting an initial patient data set since March of this year. Between March and August of 2011, 65 EIS tests were conducted on 65 patients. Among these cases, six depicted pathology-verified malignant cells. Our initial assessment indicates the feasibility of easily applying this REIS device and measurement approach in a very busy clinical setting. The measured resonance frequency differences between malignant and benign nodules could potentially make it possible to accurately classify indeterminate thyroid nodules.
Palermo, Samuel; Chiang, Patrick; Yu, Kunzhi; Bai, Rui; Li, Cheng; Chen, Chin-Hui; Fiorentino, Marco; Beausoleil, Ray; Li, Hao; Shafik, Ayman; Titriku, Alex
2016-03-01
Interconnect architectures based on high-Q silicon photonic microring resonator devices offer a promising solution to address the dramatic increase in datacenter I/O bandwidth demands due to their ability to realize wavelength-division multiplexing (WDM) in a compact and energy efficient manner. However, challenges exist in realizing efficient receivers for these systems due to varying per-channel link budgets, sensitivity requirements, and ring resonance wavelength shifts. This paper reports on adaptive optical receiver design techniques which address these issues and have been demonstrated in two hybrid-integrated prototypes based on microring drop filters and waveguide photodetectors implemented in a 130nm SOI process and high-speed optical front-ends designed in 65nm CMOS. A 10Gb/s powerscalable architecture employs supply voltage scaling of a three inverter-stage transimpedance amplifier (TIA) that is adapted with an eye-monitor control loop to yield the necessary sensitivity for a given channel. As reduction of TIA input-referred noise is more critical at higher data rates, a 25Gb/s design utilizes a large input-stage feedback resistor TIA cascaded with a continuous-time linear equalizer (CTLE) that compensates for the increased input pole. When tested with a waveguide Ge PD with 0.45A/W responsivity, this topology achieves 25Gb/s operation with -8.2dBm sensitivity at a BER=10-12. In order to address microring drop filters sensitivity to fabrication tolerances and thermal variations, efficient wavelength-stabilization control loops are necessary. A peak-power-based monitoring loop which locks the drop filter to the input wavelength, while achieving compatibility with the high-speed TIA offset-correction feedback loop is implemented with a 0.7nm tuning range at 43μW/GHz efficiency.
Directory of Open Access Journals (Sweden)
Guojun Zhang
2015-04-01
Full Text Available The MEMS vector hydrophone developed by the North University of China has advantages of high Signal to Noise Ratio, ease of array integration, etc. However, the resonance frequency of the MEMS device in the liquid is different from that in the air due to the fluid-structure interaction (FSI. Based on the theory of Fluid-Solid Coupling, a generalized distributed mass attached on the micro-structure has been found, which results in the resonance frequency of the microstructure in the liquid being lower than that in the air. Then, an FSI simulation was conducted by ANSYS software. Finally, the hydrophone was measured by using a shaking table and a vector hydrophone calibration system respectively. Results show that, due to the FSI, the resonance frequency of the MEMS devices of the bionic vector hydrophone in the liquid declines approximately 30% compared to the case in the air.
Load-adaptive frequency reuse scheme for inter-cell interference coordination in relay networks
Institute of Scientific and Technical Information of China (English)
CHEN Mu-qiong; JI Hong; LI Xi
2010-01-01
Cellular relay networks adopting orthogonal frequency division multiple(OFDM)technology has been widely accepted for next generation wireless communication due to its advantage in enlarging coverage scale as well as improving data rate.In order to improve the performance of user equipments(UEs)near the cell edge,especially to avoid the interference from inter-cell and intra cell,an enhanced soft frequency reuse scheme is adopted in this paper to assure inter-cell interference coordination(ICIC).Compared with traditional frequency allocation work,the proposed scheme is interference-aware and load-adaptive,which dynamically assigns available frequency among UES under certain schedule method in variable traffic load condition and mitigates interference using information provided by interference indicator.It can improve signal-to-interference plus noise ratio(SINR)of the UE in each sub channel thus enable the system achieve better throughput and blocking probability performance.Simulation results prove that the proposed scheme may achieve desirable performance on throughput,blocking probability and spectral utilization in the sector under different traffic load compared with other schemes.
Frequency-shift low-pass filtering and least mean square adaptive filtering for ultrasound imaging
Wang, Shanshan; Li, Chunyu; Ding, Mingyue; Yuchi, Ming
2016-04-01
Ultrasound image quality enhancement is a problem of considerable interest in medical imaging modality and an ongoing challenge to date. This paper investigates a method based on frequency-shift low-pass filtering (FSLF) and least mean square adaptive filtering (LMSAF) for ultrasound image quality enhancement. FSLF is used for processing the ultrasound signal in the frequency domain, while LMSAPF in the time domain. Firstly, FSLF shifts the center frequency of the focused signal to zero. Then the real and imaginary part of the complex data are filtered respectively by finite impulse response (FIR) low-pass filter. Thus the information around the center frequency are retained while the undesired ones, especially background noises are filtered. Secondly, LMSAF multiplies the signals with an automatically adjusted weight vector to further eliminate the noises and artifacts. Through the combination of the two filters, the ultrasound image is expected to have less noises and artifacts and higher resolution, and contrast. The proposed method was verified with the RF data of the CIRS phantom 055A captured by SonixTouch DAQ system. Experimental results show that the background noises and artifacts can be efficiently restrained, the wire object has a higher resolution and the contrast ratio (CR) can be enhanced for about 12dB to 15dB at different image depth comparing to delay-and-sum (DAS).
Low-frequency resonances of the refractive index in weakly ionized plasma with an admixture of dust
International Nuclear Information System (INIS)
The propagation of low-frequency electromagnetic waves along the magnetic field in weakly ionized plasma with an admixture of dust is studied in the framework of the Hall magnetohydrodynamics. Explicit expressions for the coefficients of magnetic field diffusion in plasma are derived. The resonance of the refractive index is found to occur for either right- or left-hand polarized waves. A quantitative criterion is obtained that allows one to determine the polarization of waves that experience resonance at given plasma parameters. The physical mechanism of the resonance is discussed, and the obtained results are compared with the available literature data
Electrostrictive resonances in (Ba0.7Sr0.3)TiO3 thin films at microwave frequencies
Tappe, S.; Bottger, U.; Waser, R.
2004-01-01
The bias-voltage-dependent permittivity of (Ba0.7Sr0.3)TiO3 (BST) thin films with thicknesses ranging from 100 to 250 nm is investigated in the frequency range from 500 MHz to 40 GHz by impedance spectroscopy of integrated BST capacitors. The dielectric spectra of the films exhibit resonance phenomena in the 4-7 GHz range when a bias field is applied. It is shown that the main controlling parameter of the resonance frequency is the film thickness. Calculations based on the strong electrostric...
International Nuclear Information System (INIS)
Numerical solution to the Schroedinger equation with open boundary conditions is found out, which makes it possible to describe coherent generation in resonant-tunneling diodes in a broad interval of frequencies and field amplitudes. Within the linear field area approximation results obtained coincide with a high degree of accuracy with analytical results. The power of generation is calculated as a function of the current and other parameters of the resonant-tunneling diode. It is demonstrated that the high-power generation is possible in the quantum regime at frequencies exceeding the level width, i. e. within the THz range
A Dual-Bridge LLC Resonant Converter with Fixed-Frequency PWM Control for Wide Input Applications
DEFF Research Database (Denmark)
Xiaofeng, Sun; Li, Xiaohua; Shen, Yanfeng;
2016-01-01
This paper proposes a dual-bridge (DB) LLC resonant converter for wide input applications. The topology is an integration of a half-bridge (HB) LLC circuit and a full-bridge (FB) LLC circuit. The fixed-frequency PWM control is employed and a range of twice the minimum input voltage can be covered....... Compared with the traditional pulse frequency modulation (PFM) controlled HB/FB LLC resonant converter, the voltage gain range is independent of the quality factor and the magnetizing inductor has little influence on the voltage gain, which can simplify the parameter selection process and benefit the...
Liu, Runnan; Wu, Ke; Kashyap, Raman
2007-06-01
The doped fiber external cavity semiconductor laser (DFECL) has been reported with a simple structure, high power, narrow linewidth, and stable wavelength. The DFECL is mostly suitable to be an optical carrier generator for external modulation or microwave optical generation. Because of mode locking, the DFECL, with saturable absorber in its external cavity, has the possibility to be direct modulated at its multiples of cavity resonant frequency. The useful modulation frequency of the laser can be increased significantly. In this paper, we present experimental results about the transmission response of direct modulation of an ultra-long DFECL, and the modulated microwave signal transmission at the frequency of the 22 nd. multiple of the cavity resonant frequency. Modulated narrow bandwidth microwave signals at 2.4GHz were transmitted by this DFECL. The received RF spectrum has no obvious distortion for a 10MHz narrow band microwave signal and, all the resonant and harmonic frequencies in the 0~2.5GHz region are 50 dB lower than the transmitted wave. The results show that narrowband modulated microwave can be transmitted at high frequency by the long DFECL; even through the cavity round-trip frequency is very low. We conclude that this ultra-long doped fiber external cavity semiconductor laser can be used for narrowband wireless communication with direct modulation.
Institute of Scientific and Technical Information of China (English)
张武; 唐锦春
2002-01-01
This paper establishes a piezoelectric constitutive computational approach based on generalized eigenvalue and multivariable finite element solutions with potential applications to accurate and effective analysis of layered piezoelectric microstructures of arbitrary geometries and different anisotropic materials, to ease the limitation of current computer capacity in analyzing large-scale high-frequency disturbed surface acoustic waves (DSAW) by mounted electrodes in piezoelectric devices such as microchip SAW resonators. A new incompatible generalized hybrid/mixed element GQM5 is also proposed for improving predictions of the piezoelectric surface mount thermal stresses that are shear-dominated. The (generalized) plane strain constitutive model is numerically verified for piezoelectric finite element computation. With the help of computational piezoelectricity (electro-mechanics) for general layered structures with metal electrodes and anisotropic piezoelectric substrates, some new interesting, reliable and fundamental constitutive finite element results are obtained for high-frequency piezoelectric and mechanical SAW propagations and can be used for further applications. The ST-cut FEA results agree quite well with available exact and lab solutions for free surface case.
Effect of non-ideal clamping shape on the resonance frequencies of silicon nanocantilevers
Energy Technology Data Exchange (ETDEWEB)
Guillon, Samuel; Saya, Daisuke; Mazenq, Laurent; Nicu, Liviu [CNRS, LAAS, 7 Avenue du Colonel Roche, F-31077 Toulouse Cedex 4 (France); Perisanu, Sorin; Vincent, Pascal [LPMCN, Universite Claude Bernard Lyon 1 et CNRS, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex (France); Lazarus, Arnaud; Thomas, Olivier, E-mail: sguillon@laas.fr [Structural Mechanics and Coupled Systems Laboratory, Conservatoire National des Arts et Metiers, 2 rue Conte, 75003 Paris (France)
2011-06-17
In this paper, we investigate the effects of non-ideal clamping shapes on the dynamic behavior of silicon nanocantilevers. We fabricated silicon nanocantilevers using silicon on insulator (SOI) wafers by employing stepper ultraviolet (UV) lithography, which permits a resolution of under 100 nm. The nanocantilevers were driven by electrostatic force inside a scanning electron microscope (SEM). Both lateral and out-of-plane resonance frequencies were visually detected with the SEM. Next, we discuss overhanging of the cantilever support and curvature at the clamping point in the silicon nanocantilevers, which generally arises in the fabrication process. We found that the fundamental out-of-plane frequency of a realistically clamped cantilever is always lower than that for a perfectly clamped cantilever, and depends on the cantilever width and the geometry of the clamping point structure. Using simulation with the finite-elements method, we demonstrate that this discrepancy is attributed to the particular geometry of the clamping point (non-zero joining curvatures and a flexible overhanging) that is obtained in the fabrication process. The influence of the material orthotropy is also investigated and is shown to be negligible.
Waves on fluid-loaded shells and their resonance frequency spectrum
DEFF Research Database (Denmark)
Bao, X.L.; Uberall, H.; Raju, P.K.;
2005-01-01
Technical requirements for elastic (metal) cylindrical shells include the knowledge of their natural frequency spectrum. These shells may be empty and fluid-immersed, or fluid-filled in an ambient medium of air, or doubly fluid-loaded inside and out. They may support circumferential waves, or axi...... axial direction if the cylindrical shell is terminated at both ends. In this way, we obtain (circumferential and axial wave) eigenfrequency spectra for water filled aluminum and steel shells, and also for brass shells (axial-wave resonances only).......Technical requirements for elastic (metal) cylindrical shells include the knowledge of their natural frequency spectrum. These shells may be empty and fluid-immersed, or fluid-filled in an ambient medium of air, or doubly fluid-loaded inside and out. They may support circumferential waves, or...... axially propagating waves both in the shell material, and in the fluid loading. Previous results by Bao et al. (J. Acoust. Soc. Am. 105 (1999) 2704) were obtained for the circumferential-wave dispersion curves on doubly loaded aluminum shells; the present study extends this to fluid-filled shells in air...
Mildice, J. W.; Schreiner, K. E.; Wolff, F.
1987-01-01
Addressed is a class of resonant power processing equipment designed to be used in an integrated high frequency (20 KHz domain), utility power system for large, multi-user spacecraft and other aerospace vehicles. It describes a hardware approach, which has been the basis for parametric and physical data used to justify the selection of high frequency ac as the PMAD baseline for the space station. This paper is part of a larger effort undertaken by NASA and General Dynamics to be sure that all potential space station contractors and other aerospace power system designers understand and can comfortably use this technology, which is now widely used in the commercial sector. In this paper, we will examine control requirements, stability, and operational modes; and their hardware impacts from an integrated system point of view. The current space station PMAD system will provide the overall requirements model to develop an understanding of the performance of this type of system with regard to: (1) regulation; (2) power bus stability and voltage control; (3) source impedance; (4) transient response; (5) power factor effects; and (6) limits and overloads.
Ruchko, L F; Elfimov, A G; Teixeira, C M; Elizondo, J I; Sanada, E; Galvão, R M O; Manso, M E; Silva, A
2011-02-01
A frequency scanning O-mode reflectometer was used for studies of plasma density oscillations during local Alfvén wave (LAW) excitation in the Tokamak Chauffage Alfvén Brésilien (TCABR) at the frequency f(A) = 5 MHz. It was found that the spectrum of the reflectometer output signal, which consists mainly of the "beat" frequency f(B), is modified by the LAW excitation, and two additional frequency peaks appear, which are symmetrical in relation to the LAW excitation frequency f = f(A) ± f(B). This result opens the possibility to improve the efficiency of studying the LAW induced density oscillations. The symmetry of these frequency peaks yields the possibility of finding the microwave frequency at which the reflectometer cutoff layer coincides with radial position of the LAW resonance zone in the TCABR tokamak.
Ruchko, L. F.; Elfimov, A. G.; Teixeira, C. M.; Elizondo, J. I.; Sanada, E.; Galvão, R. M. O.; Manso, M. E.; Silva, A.
2011-02-01
A frequency scanning O-mode reflectometer was used for studies of plasma density oscillations during local Alfvén wave (LAW) excitation in the Tokamak Chauffage Alfvén Brésilien (TCABR) at the frequency fA = 5 MHz. It was found that the spectrum of the reflectometer output signal, which consists mainly of the "beat" frequency fB, is modified by the LAW excitation, and two additional frequency peaks appear, which are symmetrical in relation to the LAW excitation frequency f = fA ± fB. This result opens the possibility to improve the efficiency of studying the LAW induced density oscillations. The symmetry of these frequency peaks yields the possibility of finding the microwave frequency at which the reflectometer cutoff layer coincides with radial position of the LAW resonance zone in the TCABR tokamak.
Zektzer, Roy; Stern, Liron; Mazurski, Noa; Levy, Uriel
2016-07-01
Stabilized laser lines are highly desired for myriad of applications ranging from precise measurements to optical communications. While stabilization can be obtained by using molecular or atomic absorption references, these are limited to specific frequencies. On the other hand, resonators can be used as wide band frequency references. Unfortunately, such resonators are unstable and inaccurate. Here, we propose and experimentally demonstrate a chip-scale multispectral frequency standard replication operating in the spectral range of the near IR. This is obtained by frequency locking a microring resonator (MRR) to an acetylene absorption line. The MRR consists of a Si3N4 waveguides with microheater on top of it. The thermo-optic effect is utilized to lock one of the MRR resonances to an acetylene line. This locked MRR is then used to stabilize other laser sources at 980 nm and 1550 nm wavelength. By beating the stabilized laser to another stabilized laser, we obtained frequency instability floor of 4 ×10-9 at around 100 s in terms of Allan deviation. Such stable and accurate chip scale sources are expected to serve as important building block in diverse fields such as communication and metrology.
Directory of Open Access Journals (Sweden)
Taranov D. M.
2015-06-01
Full Text Available This article presents main water supply systems and justifies the choice of direct flow of water supply system in the application of regulation of electric drive for pumps, which doesn’t have any tanks to create pressures required for fire-governmental purposes. This avoids interruption in the supply of reserve while water freezing. In the article the substantiation of the necessity of implementation of adaptive algorithm in modern-WIDE frequency converters by a substantiation of the number of stages of ratio control of voltage-frequency mains. It was revealed that the number of degrees of regulation of 10-12 gives optimum. Modern frequency converters allow you to change the regulation law, establishing 3-5 points of regulation. Therefore, the introduction of adaptive algorithm will reduce the power consumption of the electric drive of the pump of the water supply system. The article shows the simulation model of the "the converter frequency-induction motor," plots of the stator current of mains frequency and active power, surface speed and phase current when changing the voltage and frequency of the mains. These dependences confirm to have applicability of adaptive algorithm in the regulation of modern frequency converters with the skalar administration. Simulation model confirms the sub-physical experiments on a real motor and frequency converter with adaptive control algorithm. As a result of the selection of the parameters, we obtain the voltage reduction of the phase current, and reduce electricity consumption by 5-7%
Koelsch, Patrick; Muglali, Mutlu; Rohwerder, Michael; Erbe, Andreas
2013-01-01
Vibrational sum-frequency-generation (SFG) spectroscopy experiments at electrified interfaces involve incident laser radiation at frequencies in the IR and near-IR/visible regions as well as a static electric field on the surface. Here we show that mixing the three fields present on the surface can result in third-order effects in resonant SFG signals. This was achieved for closed packed self-assembled monolayers (SAMs) with molecular groups of high optical nonlinearity and surface potentials...
Radeva, Ekaterina I.; Esmeryan, Karekin D.; Ivan D. Avramov
2012-01-01
Temperature induced frequency shifts may compromise the sensor response of polymer coated acoustic wave gas-phase sensors operating in environments of variable temperature. To correct the sensor data with the temperature response of the sensor the latter must be known. This study presents and discusses temperature frequency characteristics (TFCs) of solid hexamethyldisiloxane (HMDSO) polymer coated sensor resonators using the Rayleigh surface acoustic wave (RSAW) mode on ST-cut quartz. Using ...
Directory of Open Access Journals (Sweden)
Jong-Seob Baek
2008-01-01
Full Text Available This paper presents a new block iterative/adaptive frequency-domain channel estimation scheme, in which a channel frequency response (CFR is estimated iteratively by the proposed weighted element-wise block adaptive frequency-domain channel estimation (WEB-CE scheme using the soft information obtained by a soft-input soft-output (SISO decoder. In the WEB-CE, an equalizer coefficient is calculated by minimizing a weighted conditional squared-norm of the a posteriori error vector with respect to its correction term. Simulation results verify the superiority of the WEB-CE in a time-varying typical urban (TU channel.
Sollner, T. C. L. G.; Brown, E. R.; Goodhue, W. D.; Le, H. Q.
1987-01-01
Recent observations of oscillation frequencies up to 56 GHz in resonant tunneling structures are discussed in relation to calculations by several authors of the ultimate frequency limits of these devices. It is found that calculations relying on the Wentzel-Kramers-Brillouin (WKB) approximation give limits well below the observed oscillation frequencies. Two other techniques for calculating the upper frequency limit were found to give more reasonable results. One method employs the solution of the time-dependent Schroedinger equation obtained by Kundrotas and Dargys (1986); the other uses the energy width of the transmission function for electrons through the double-barrier structure. This last technique is believed to be the most accurate since it is based on general results for the lifetime of any resonant state. It gives frequency limits on the order of 1 THz for two recently fabricated structures. It appears that the primary limitation of the oscillation frequency for double-barrier resonant-tunneling diodes is imposed by intrinsic device circuit parameters and by the transit time of the depletion layer rather than by time delays encountered in the double-barrier region.
Green, red and IR frequency comb line generation from single IR pump in AlN microring resonator
Jung, Hojoong; Guo, Xiang; Fischer, Debra; Tang, Hong X
2014-01-01
On-chip frequency comb generations enable compact broadband sources for spectroscopic sensing and precision spectroscopy. Recent microcomb studies focus on infrared spectral regime and have difficulty in accessing visible regime. Here, we demonstrate comb-like visible frequency line generation through second, third harmonic, and sum frequency conversion of a Kerr comb within a high Q aluminum nitride microring resonator pumped by a single telecom laser. The strong power enhancement, in conjunction with the unique combination of Pockels and Kerr optical nonlinearity of aluminum nitride, leads to cascaded frequency conversions in the visible spectrum. High-resolution spectroscopic study of the visible frequency lines indicates matched free spectrum range over all the bands. This frequency doubling and tripling effect in a single microcomb structure offers great potential for comb spectroscopy and self-referencing comb.
DEFF Research Database (Denmark)
Liu, Qing Zhong
1992-01-01
Unified analytical expressions have been derived for calculating the resonant frequencies, transimpedance and equivalent input noise current densities of the four most widely used tuned optical receiver front ends built with FETs and p-i-n diodes. A more accurate FET model has been used to improve...
Orlinkskii, S.B.; Borovykh, I.V.; Zielke, V.; Steinhoff, H.J.
2007-01-01
The applicability of spin labels to study membrane proteins by high-frequency electron nuclear double resonance spectroscopy is demonstrated. With the use of bacteriorhodopsin embedded in a lipid membrane as an example, the spectra of protons of neighboring amino acids are recorded, electric field g
Ainslie, M.A.; Leighton, T.G.
2011-01-01
Perhaps the most familiar concepts when discussing acoustic scattering by bubbles are the resonance frequency for bubble pulsation, the bubbles' damping, and their scattering and extinction cross-sections, all of which are used routinely in oceanography, sonochemistry, and biomedicine. The apparent
Directory of Open Access Journals (Sweden)
Youngsoo Jang
2013-01-01
Full Text Available A capacitor-loaded electrical small zeroth-order resonant (ZOR antenna is proposed. The proposed antenna is designed on the basis of a mushroom structure for zeroth-order resonance. To obtain a compact size, the proposed antenna has a rectangular slot on the ground plane, and the chip capacitor is mounted on the slot. The resonant frequency is easily controlled from 2.82 GHz to 2.29 GHz by changing the capacitance from 1 pF to 7 pF, respectively. Therefore, the proposed antenna has the advantages of a small antenna size as well as easy frequency adjustment.
Adaptive grid artifact reduction in the frequency domain with spatial properties for x-ray images
Kim, Dong Sik; Lee, Sanggyun
2012-03-01
By applying band-rejection filters (BRFs) in the frequency domain, we can efficiently reduce the grid artifacts, which are caused by using the antiscatter grid in obtaining x-ray digital images. However, if the frequency component of the grid artifact is relatively close to that of the object, then simply applying a BRF may seriously distort the object and cause the ringing artifacts. Since the ringing artifacts are quite dependent on the shape of the object to be recovered in the spatial domain, the spatial property of the x-ray image should be considered in applying BRFs. In this paper, we propose an adaptive filtering scheme, which can cooperate such different properties in the spatial domain. In the spatial domain, we compare several approaches, such as the mangnitude, edge, and frequency-modulation (FM) model-based algorithms, to detect the ringing artifact or the grid artifact component. In order to perform a robust detection whether the ringing artifact is strong or not, we employ the FM model for the extracted signal, which corresponds to a specific grid artifact. A detection of the position for the ringing artifact is then conducted based on the slope detection algorithm, which is commonly used as an FM discriminator in the communication area. However, the detected position of the ringing artifact is not accurate. Hence, in order to obtain an accurate detection result, we combine the edge-based approach with the FM model approach. Numerical result for real x-ray images shows that applying BRFs in the frequency domain in conjunction with the spatial property of the ringing artifact can successfully remove the grid artifact, distorting the object less.
Institute of Scientific and Technical Information of China (English)
Wang Gang; Liu Yao-Zong; Wen Ji-Hong; Yu Dian-Long
2006-01-01
The low-frequency band gap and the corresponding vibration modes in two-dimensional ternary locally resonant phononic crystals are restudied successfully with the lumped-mass method. Compared with the work of C. Goffaux and J. Sanchez-Dehesa (Phys. Rev. B 67 14 4301(2003)), it is shown that there exists an error of about 50% in their calculated results of the band structure, and one band is missing in their results. Moreover, the in-plane modes shown in their paper are improper, which results in the wrong conclusion on the mechanism of the ternary locally resonant phononic crystals. Based on the lumped-mass method and better description of the vibration modes according to the band gaps, the locally resonant mechanism in forming the subfrequency gaps is thoroughly analysed. The rule used to judge whether a resonant mode in the phononic crystals can result in a corresponding subfrequency gap is also verified in this ternary case.
International Nuclear Information System (INIS)
Purpose: To analyse the frequency of patients with absolute and relative contraindications to magnetic resonance (MR) imaging who were actually referred to an outpatient imaging centre for an MR examination Materials and methods: Altogether a total of 51,547 consecutive patients were included between November 1997 and December 2005. Reasons preventing MR imaging were classified into the following categories: absolute and relative contraindications. Results: The referral frequency of patients with absolute contraindications to MR imaging was 0.41% (211 of 51,547 patients; 95% CI, 0.36-0.47%). The absolute contraindications were shrapnels located in biologically sensitive areas (121 patients, 0.23%; 95% CI, 0.20-0.28%), cardiac pacemakers (42 patients, 0.08%; 95% CI, 0.06-0.11%), and other unsafe implants (48 patients, 0.09%; 95% CI, 0.07-0.12%). Also patients with a relative contraindication to MR imaging were referred such as women with a first-trimester pregnancy (13 patients, 0.03%; 95% CI, 0.01-0.04%). Conclusion: Surprisingly, a considerable number of patients (0.41%) with cardiac pacemakers, other metallic implants (not approved for MR), or shrapnels are referred to MR facilities despite the well-known recommendations not to examine such patients. Thus, absolute contraindications to MR imaging are commonly found among patients referred for MR examinations and every effort needs to be made to screen patients prior to MR imaging for such contraindications to avoid detrimental results. Also, institutions placing implants (approved and unapproved for MR) should become legally responsible for providing the required information to the patients and their physicians
An Adaptive Controller Based upon Continuous Estimation of the Closed Loop Frequency Response
Directory of Open Access Journals (Sweden)
Jens G. Balchen
1987-10-01
Full Text Available An adaptive control algorithm based upon on-line estimation of the -180 degree shift frequency and the gain margin is investigated. The estimates are found by perturbing the system with a small signal and then correlating the system deviation with the excitation. As only two parameters are estimated, the algorithm is robust. Moreover, the estimator can be applied to non-minimum phase systems, including systems with a varying time-delay. The control algorithm can be of any form as long as there is a functional relationship between the estimated parameters and the control algorithm parameters. To avoid an excessive perturbation signal, the square of the amplitude of this signal is automatically adjusted to a certain ratio of the variance of the error signal. A mathematical analysis of convergence is presented and the theory is confirmed by experimental results.
Directory of Open Access Journals (Sweden)
Krishnan Sridhar
2007-01-01
Full Text Available This paper introduces a novel algorithm to excise single and multicomponent chirp-like interferences in direct sequence spread spectrum (DSSS communications. The excision algorithm consists of two stages: adaptive signal decomposition stage and directional element detection stage based on the Hough-Radon transform (HRT. Initially, the received spread spectrum signal is decomposed into its time-frequency (TF functions using an adaptive signal decomposition algorithm, and the resulting TF functions are mapped onto the TF plane. We then use a line detection algorithm based on the HRT that operates on the image of the TF plane and detects energy varying directional elements that satisfy a parametric constraint. Interference is modeled by reconstructing the corresponding TF functions detected by the HRT, and subtracted from the received signal. The proposed technique has two main advantages: (i it localizes the interferences on the TF plane with no cross-terms, thus facilitating simple filtering techniques based on thresholding of the TF functions, and is an efficient way to excise the interference; (ii it can be used for the detection of any directional interferences that can be parameterized. Simulation results with synthetic models have shown successful performance with linear and quadratic chirp interferences for single and multicomponent interference cases. The proposed method excises the interference even under very low SNR conditions of dB, and the technique could be easily extended to any interferences that could be represented by a parametric equation in the TF plane.
Multi-frequency electron paramagnetic resonance study of irradiated human finger phalanxes
Zdravkova, M.; Vanhaelewyn, G.; Callens, F.; Gallez, B.; Debuyst, R.
2005-10-01
Electron paramagnetic resonance (EPR) is often used in dosimetry using biological samples such as teeth and bones. It is generally assumed that the radicals, formed after irradiation, are similar in both tissues as the mineral part of bone and tooth is carbonated hydroxyapatite. However, there is a lack of experimental evidence to support this assumption. The aim of the present study was to contribute to that field by studying powder and block samples of human finger phalanxes that were irradiated and analyzed by multi-frequency EPR. The results obtained from bones are different from the ones obtained in enamel by several respects: the ordering of the apatite crystallites is much smaller in bone, complicating the assignment of the observed CO 2- radicals to a specific location, and one type of CO 33- radical was only found in enamel. Moreover, a major difference was found in the non-CO 2- and non-CO 33- signals. The elucidation of the nature of these native signals (in bone and tooth enamel) still represents a big challenge.
Directory of Open Access Journals (Sweden)
Fretz Christian
2010-02-01
Full Text Available Abstract Background Radio Frequency Identification (RFID devices are becoming more and more essential for patient safety in hospitals. The purpose of this study was to determine patient safety, data reliability and signal loss wearing on skin RFID devices during magnetic resonance imaging (MRI and computed tomography (CT scanning. Methods Sixty RFID tags of the type I-Code SLI, 13.56 MHz, ISO 18000-3.1 were tested: Thirty type 1, an RFID tag with a 76 × 45 mm aluminum-etched antenna and 30 type 2, a tag with a 31 × 14 mm copper-etched antenna. The signal loss, material movement and heat tests were performed in a 1.5 T and a 3 T MR system. For data integrity, the tags were tested additionally during CT scanning. Standardized function tests were performed with all transponders before and after all imaging studies. Results There was no memory loss or data alteration in the RFID tags after MRI and CT scanning. Concerning heating (a maximum of 3.6°C and device movement (below 1 N/kg no relevant influence was found. Concerning signal loss (artifacts 2 - 4 mm, interpretability of MR images was impaired when superficial structures such as skin, subcutaneous tissues or tendons were assessed. Conclusions Patients wearing RFID wristbands are safe in 1.5 T and 3 T MR scanners using normal operation mode for RF-field. The findings are specific to the RFID tags that underwent testing.
High-frequency electro-optic measurement of strained silicon racetrack resonators.
Borghi, M; Mancinelli, M; Merget, F; Witzens, J; Bernard, M; Ghulinyan, M; Pucker, G; Pavesi, L
2015-11-15
The observation of the electro-optic effect in strained silicon waveguides has been considered a direct manifestation of an induced χ(2) nonlinearity in the material. In this work, we perform high-frequency measurements on strained silicon racetrack resonators. Strain is controlled by a mechanical deformation of the waveguide. It is shown that any optical modulation vanishes, independent of the applied strain, when the applied voltage varies much faster than the carrier effective lifetime and that the DC modulation is also largely independent of the applied strain. This demonstrates that plasma carrier dispersion is responsible for the observed electro-optic effect. After normalizing out free-carrier effects, our results set an upper limit of (8±3) pm/V to the induced high-speed effective χeff,zzz(2) tensor element at an applied stress of -0.5 GPa. This upper limit is about 1 order of magnitude lower than previously reported values for static electro-optic measurements. PMID:26565856
High frequency electro-optic measurement of strained silicon racetrack resonators
Borghi, M; Merget, F; Witzens, J; Bernard, M; Ghulinyan, M; Pucker, G; Pavesi, L
2015-01-01
The observation of the electro-optic effect in strained silicon waveguides has been considered as a direct manifestation of an induced $\\chi^{(2)}$ non-linearity in the material. In this work, we perform high frequency measurements on strained silicon racetrack resonators. Strain is controlled by a mechanical deformation of the waveguide. It is shown that any optical modulation vanishes independently of the applied strain when the applied voltage varies much faster than the carrier effective lifetime, and that the DC modulation is also largely independent of the applied strain. This demonstrates that plasma carrier dispersion is responsible for the observed electro-optic effect. After normalizing out free carrier effects, our results set an upper limit of $8\\,pm/V$ to the induced high-speed $\\chi^{(2)}_{eff,zzz}$ tensor element at an applied stress of $-0.5\\,GPa$. This upper limit is about one order of magnitude lower than the previously reported values for static electro-optic measurements.
Zhao, Jinkui; Hamilton, William A.; Lee, Sung-Woo; Robertson, J. L.; Crow, Lowell; Kang, Yoon W.
2015-09-01
The analysis of neutron diffraction experiments often assumes that neutrons are elastically scattered from the sample. However, there is growing evidence that a significant fraction of the detected neutrons is in fact inelastically scattered, especially from soft materials and aqueous samples. Ignoring these inelastic contributions gives rise to inaccurate experimental results. To date, there has been no simple method with broad applicability for inelastic signal separation in neutron diffraction experiments. Here, we present a simple and robust method that we believe could be suited for this purpose. We use two radio frequency resonant spin flippers integrated with a Larmor precession field to modulate the neutron intensity and to encode the inelastic scattering information into the neutron data. All three components contribute to the spin encoding. The Larmor field serves several additional purposes. Its usage facilitates neutron time-focusing, eliminates the need for stringent magnetic shielding, and allows for compact setups. The scheme is robust, simple, and flexible. We believe that, with further improvements, it has the potential of adding inelastic signal discrimination capabilities to many existing diffraction instruments in the future.
International Nuclear Information System (INIS)
Modulated high frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low frequency (ELF)/very low frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high energy electrons. Combining the ray tracing method and test particle simulations, we evaluate the effects of energetic electron resonant scattering driven by the discrete, multi-frequency artificially generated ELF/VLF waves. The simulation results indicate a stochastic behavior of electrons and a linear profile of pitch angle and kinetic energy variations averaged over all test electrons. These features are similar to those associated with single-frequency waves. The computed local diffusion coefficients show that, although the momentum diffusion of relativistic electrons due to artificial ELF/VLF whistlers with a nominal amplitude of ∼ 1 pT is minor, the pitch angle scattering can be notably efficient at low pitch angles near the loss cone, which supports the feasibility of artificial triggering of multi-frequency ELF/VLF whistler waves for the removal of high energy electrons from the magnetosphere. We also investigate the dependences of diffusion coefficients on the frequency interval (Δf) of the discrete, multi-frequency waves. We find that there is a threshold value of Δf for which the net diffusion coefficient of multi-frequency whistlers is inversely proportional to Δf (proportional to the frequency components Nw) when Δf is below the threshold value but it remains unchanged with increasing Δf when Δf is larger than the threshold value. This is explained as being due to the fact that the resonant scattering effect of broadband waves is the sum of the effects of each frequency in the ‘effective frequency band’. Our results suggest that the modulation frequency of HF heating of the ionosphere can be appropriately selected with reasonable frequency intervals so that better
Grossberg, Stephen; Kazerounian, Sohrob
2016-08-01
Magnuson [J. Acoust. Soc. Am. 137, 1481-1492 (2015)] makes claims for Interactive Activation (IA) models and against Adaptive Resonance Theory (ART) models of speech perception. Magnuson also presents simulations that claim to show that the TRACE model can simulate phonemic restoration, which was an explanatory target of the cARTWORD ART model. The theoretical analysis and review herein show that these claims are incorrect. More generally, the TRACE and cARTWORD models illustrate two diametrically opposed types of neural models of speech and language. The TRACE model embodies core assumptions with no analog in known brain processes. The cARTWORD model defines a hierarchy of cortical processing regions whose networks embody cells in laminar cortical circuits as part of the paradigm of laminar computing. cARTWORD further develops ART speech and language models that were introduced in the 1970s. It builds upon Item-Order-Rank working memories, which activate learned list chunks that unitize sequences to represent phonemes, syllables, and words. Psychophysical and neurophysiological data support Item-Order-Rank mechanisms and contradict TRACE representations of time, temporal order, silence, and top-down processing that exhibit many anomalous properties, including hallucinations of non-occurring future phonemes. Computer simulations of the TRACE model are presented that demonstrate these failures. PMID:27586743
Energy Technology Data Exchange (ETDEWEB)
Berthelot, J.M.; Maugars, Y.; Delecrin, Y.; Caillon, F.; Prost, A. [Hopital Hotel-Dieu de Nantes, 44 (France)
1995-10-01
Magnetic resonance imaging (MRI) has had an impressive impact on evaluation of degenerative diseases of the spine. Nevertheless, false negatives can occur on images involving lumbar discs. Degenerative disc diseases documented on discography and/or pathology examination of the discs can go unrecognized. Likewise sensitivity for the detection of protruding disc hernias is not totally satisfactory (20% false negatives). Finally, a magnetic resonance image visualizing displacement of the disc is not specific (10 to 15% false positives); images showing protrusion or hernia can be seen in 30% of asymptomatic patients. Although MRI gives slightly more information than other imaging techniques, false images do exist. Moreover, the usefulness of MRI to demonstrate disc disease in case of a negative CT-scan remains to be demonstrated. (authors). 26 refs.
Ding, Yujie J
2015-03-01
Raman oscillation, frequency upconversion, and Raman amplification can be achieved in a second-order nonlinear medium at the phonon-polariton resonance. By beating two optical fields, a second-order nonlinear polarization is generated inside the medium. Such a polarization induces a spatially uniform nonpropagating electric field at the beat frequency, which in turn mixes with the input optical field at the lower frequency to generate or amplify the anti-Stokes optical field. Raman oscillation can be efficiently reached for the copropagating configuration. In comparison, efficient frequency upconversion and large amplifications are achievable for the counterpropagating configuration. These Raman processes can be used to effectively remove transverse-optical phonons before decaying to lower-frequency phonons, achieve laser cooling, and significantly enhance coherent anti-Stokes Raman scattering. The counterpropagating configuration offers advantages for amplifying extremely weak signals. PMID:25723418
Cheng, Y; Zhou, C; Yuan, B G; Wu, D J; Wei, Q; Liu, X J
2015-10-01
Acoustic metamaterials offer great flexibility for manipulating sound waves and promise unprecedented functionality, ranging from transformation acoustics, super-resolution imaging to acoustic cloaking. However, the design of acoustic metamaterials with exciting functionality remains challenging with traditional approaches using classic acoustic elements such as Helmholtz resonators and membranes. Here we demonstrate an ultraslow-fluid-like particle with intense artificial Mie resonances for low-frequency airborne sound. Eigenstate analysis and effective parameter retrieval show two individual negative bands in the single-size unit cell, one of which exhibits a negative bulk modulus supported by the monopolar Mie resonance, whereas the other exhibits a negative mass density induced by the dipolar Mie resonance. The unique single-negative nature is used to develop an ultra-sparse subwavelength metasurface with high reflectance for low-frequency sound. We demonstrate a 0.15λ-thick, 15%-filling ratio metasurface with an insertion loss over 93.4%. The designed Mie resonators provide diverse routes to construct novel acoustic devices with versatile applications. PMID:26322718
Kato, Fumihito; Ogi, Hirotsugu; Yanagida, Taiji; Nishikawa, Shintaro; Nishiyama, Masayoshi; Hirao, Masahiko
2011-07-01
We present a high-frequency electrodeless quartz crystal microbalance (QCM) chip with a bare quartz resonator encapsulated in a silicon microchannel, which is fabricated by micromachining technology. This QCM chip packages an AT-cut quartz plate 2.5 mm long, 1.7 mm wide, and 9.6 µm thick, which is supported by micropillars without fixed parts. There is no issue about destruction during assembly because handling the fragile quartz resonator becomes unnecessary. The quartz resonator is electrodeless and not fixed; therefore, there are no losses due to electrodes and contacting wires. As a result, a high quality factor (Q-factor) and a high signal-to-noise ratio (SNR) can be obtained. The Q-factor is about 800-2800 at 170 MHz in the flow of the carrier solution. In addition, it is possible to reuse the device, because the quartz surfaces can adsorb receptor proteins nonspecifically, which can be removed by a washing procedure with a strong acid solution flowed in the microchannel. The high-frequency quartz resonator (170 MHz) encapsulated in the microchannel can reduce the influence of the viscosity contribution to the frequency shift, achieving highly sensitive and quantitative analysis. The QCM chip is excited and detects the shear vibrations of the quartz resonator by the line antennas without contact. Consequently, both sides of the quartz resonator can be used as the detection area in a solution. We succeeded in detecting the human immunoglobulin G (hIgG) at a concentration of 6 µg/ml via the staphylococcal protein A (SPA) immobilized nonspecifically on the developed QCM chip in real time without any labeling.
Variations of the Magnetosphere Resonance Frequencies During Magnetic Storm of July 15——16, 2000
Institute of Scientific and Technical Information of China (English)
A. Potapov; A. Polyakov; T. Polyushkina; H. Zhao
2005-01-01
ULF observations at two mid-latitude sites during the large geomagnetic storm of July 15-16,2000 were used to trace variations of resonance frequencies of the field line resonators. A brief description of the geomagnetic disturbance as it was observed on the ground, at the geostationary orbit, and before the Earth's bow shock is given. Then a detailed study of ULF dynamic spectra from Borok and Mondy is performed for8 succesive 6-hour intervals of July 15 and 16. In conclusion some tasks for the future work are listed.
Rooze, Joost; Rebrov, Evgeny V; Schouten, Jaap C; Keurentjes, Jos T F
2011-01-01
The sonochemical oxidation efficiency (η(ox)) of a commercial titanium alloy ultrasound horn has been measured using potassium iodide as a dosimeter at its main resonance frequency (20 kHz) and two higher resonance frequencies (41 and 62 kHz). Narrow power and frequency ranges have been chosen to minimise secondary effects such as changing bubble stability, and time available for radical diffusion from the bubble to the liquid. The oxidation efficiency, η(ox), is proportional to the frequency and to the power transmitted to the liquid (275 mL) in the applied power range (1-6 W) under argon. Luminol radical visualisation measurements show that the radical generation rate increases and a redistribution of radical producing zones is achieved at increasing frequency. Argon, helium, air, nitrogen, oxygen, and carbon dioxide have been used as saturation gases in potassium iodide oxidation experiments. The highest η(ox) has been observed at 5 W under air at 62 kHz. The presence of carbon dioxide in air gives enhanced nucleation at 41 and 62 kHz and has a strong influence on η(ox). This is supported by the luminol images, the measured dependence of η(ox) on input power, and bubble images recorded under carbon dioxide. The results give insight into the interplay between saturation gas and frequency, nucleation, and their effect on η(ox). PMID:20573535
Energy Technology Data Exchange (ETDEWEB)
Deneuville, Francois; Duquennoy, Marc; Ouaftouh, Mohammadi; Jenot, Frederic; Ourak, Mohamed [IEMN-DOAE (UMR CNRS 8520), Universite de Valenciennes, 59313 Valenciennes cedex 9 (France); Desvaux, Sebastien [SKF Aeroengine France, Z. I. no. 2, Rouvignies, 59309 Valenciennes (France)
2009-05-15
A coupled analysis of high and low frequency resonant ultrasound spectroscopy of spheroidal modes is presented in this paper. Experimentally, by using an ultrasonic probe for the excitation (piezoelectric transducer) and a heterodyne optic probe for the receiver (interferometer), it was possible to take spectroscopic measurements of spheroidal vibrations over a large frequency range of 100 kHz-45 MHz in a continuous regime. This wide analysis range enabled variations in velocity due to the presence of defects to be differentiated from the inherent characteristics of the balls and consequently, it offers the possibility of detecting cracks independently of production variations. This kind of defect is difficult to detect because the C-shaped surface crack is very small and narrow (500x5 {mu}m{sup 2}), and its depth does not exceed 50 {mu}m. The proposed methodology can excite spheroidal vibrations in the ceramic balls and detect such vibrations over a large frequency range. On the one hand, low frequency resonances are used in order to estimate the elastic coefficients of the balls according to various inspection depths. This method has the advantage of providing highly accurate evaluations of the elastic coefficients over a wide frequency range. On the other hand, high frequency vibrations are considered because they are similar to the surface waves propagating in the surface zone of the ceramic balls and consequently can be used to detect C-crack defects.
DEFF Research Database (Denmark)
Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede
2016-01-01
the instantaneous grid information (e.g., frequency and phase of the grid voltage) for the current control, which is commonly performed by a Phase-Locked-Loop (PLL) system. Hence, harmonics and deviations in the estimated frequency by the PLL could lead to current tracking performance degradation, especially......Grid-connected power converters should employ advanced current controllers, e.g., Proportional Resonant (PR) and Repetitive Controllers (RC), in order to produce high-quality feed-in currents that are required to be synchronized with the grid. The synchronization is actually to detect...... of the resonant controllers and by approximating the fractional delay using a Lagrange interpolating polynomial for the RC, respectively, the frequency-variation-immunity of these periodic current controllers with a fixed sampling rate is improved. Experiments on a single-phase grid-connected system are presented...
International Nuclear Information System (INIS)
Heating with electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is a well-established method for auxiliary heating of present-day tokamak plasmas and is envisaged as one of the main heating techniques for the International Thermonuclear Experimental Reactor (ITER) and future reactor plasmas. In order to predict the performance of ICRF heating in future machines, it is important to benchmark present theoretical modelling with experimental results on present tokamaks. This thesis reports on development and experimental evaluation of theoretical models for ICRF heating at the Joint European Torus (JET). Several ICRF physics effects and scenarios have been studied. Direct importance to the ITER is the theoretical analysis of ICRF heating experiments with deuterium-tritium (D-T) plasmas. These experiments clearly demonstrate the potential of ICRF heating for auxiliary heating of reactor plasmas. In particular, scenarios with potential for good bulk ion heating and enhanced D-T fusion reactivity have been identified. Good bulk ion heating is essential for reactor plasmas in order to obtain a high ion temperature and a high fusion reactivity. In JET good bulk ion heating with ICRF waves has been achieved in high-performance discharges by adding ICRF heating to neutral beam injection. In these experiments, as in other JET discharges where damping at higher harmonics of the ion cyclotron frequency takes place, so-called finite Larmor radius (FLR) effects play an important role. Due to FLR effects, the resonating ion velocity distribution function can have a strong influence on the power deposition. Evidence for this effect has been obtained from the third harmonic deuterium heating experiments. Because of FLR effects, the wave-particle interaction can also become weak at certain ion energies, which prevents resonating ions from reaching higher energies. When interacting with the wave, an ion receives not only a change in energy but also a change in
Energy Technology Data Exchange (ETDEWEB)
Mantsinen, M. [Helsinki Univ. of Technology, Espoo (Finland). Dept. of Technical Physics
1999-06-01
Heating with electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is a well-established method for auxiliary heating of present-day tokamak plasmas and is envisaged as one of the main heating techniques for the International Thermonuclear Experimental Reactor (ITER) and future reactor plasmas. In order to predict the performance of ICRF heating in future machines, it is important to benchmark present theoretical modelling with experimental results on present tokamaks. This thesis reports on development and experimental evaluation of theoretical models for ICRF heating at the Joint European Torus (JET). Several ICRF physics effects and scenarios have been studied. Direct importance to the ITER is the theoretical analysis of ICRF heating experiments with deuterium-tritium (D-T) plasmas. These experiments clearly demonstrate the potential of ICRF heating for auxiliary heating of reactor plasmas. In particular, scenarios with potential for good bulk ion heating and enhanced D-T fusion reactivity have been identified. Good bulk ion heating is essential for reactor plasmas in order to obtain a high ion temperature and a high fusion reactivity. In JET good bulk ion heating with ICRF waves has been achieved in high-performance discharges by adding ICRF heating to neutral beam injection. In these experiments, as in other JET discharges where damping at higher harmonics of the ion cyclotron frequency takes place, so-called finite Larmor radius (FLR) effects play an important role. Due to FLR effects, the resonating ion velocity distribution function can have a strong influence on the power deposition. Evidence for this effect has been obtained from the third harmonic deuterium heating experiments. Because of FLR effects, the wave-particle interaction can also become weak at certain ion energies, which prevents resonating ions from reaching higher energies. When interacting with the wave, an ion receives not only a change in energy but also a change in
Elazab, Ahmed; Wang, Changmiao; Jia, Fucang; Wu, Jianhuang; Li, Guanglin; Hu, Qingmao
2015-01-01
An adaptively regularized kernel-based fuzzy C-means clustering framework is proposed for segmentation of brain magnetic resonance images. The framework can be in the form of three algorithms for the local average grayscale being replaced by the grayscale of the average filter, median filter, and devised weighted images, respectively. The algorithms employ the heterogeneity of grayscales in the neighborhood and exploit this measure for local contextual information and replace the standard Euclidean distance with Gaussian radial basis kernel functions. The main advantages are adaptiveness to local context, enhanced robustness to preserve image details, independence of clustering parameters, and decreased computational costs. The algorithms have been validated against both synthetic and clinical magnetic resonance images with different types and levels of noises and compared with 6 recent soft clustering algorithms. Experimental results show that the proposed algorithms are superior in preserving image details and segmentation accuracy while maintaining a low computational complexity.
Magnetic resonance micro-imaging of the human skin in vivo using miniature radio frequency coils
International Nuclear Information System (INIS)
Magnetic resonance imaging (MRI) has developed to one of the backbones of modern medical diagnostics since its first use in the 1970s. The large number of different image contrasts and the possibility to assess clinically relevant physiological parameters, especially for soft tissues, combined with the non-invasiveness and safety of the technique have been the basis for its great success. Nevertheless, is a relatively insensitive method, since it can only detect signal from a small fraction of the spins available in the investigated tissues. The higher the spatial resolution of the experiment, the lower the number of spins that effectively contribute to the signal that is acquired. This is especially critical for MR micro-imaging with voxel volumes that are about 1000-fold smaller than for standard imaging techniques. This intrinsic loss in signal can be partially recovered by operating at higher field strength, using more sensitive radio frequency detectors and optimized hardware and acquisition strategies. In this work, a combination of all these aspects has been achieved, in order to depict the network of small blood vessels in the human skin of living subjects. The demonstrated techniques allow for acquisition of a volume covering all skin layers in an area of ∼ 2 cm2 with isotropic voxel sizes of 80-100 μm in about 10 minutes. Dedicated post-processing algorithms have been developed for higher specificity of vessel detection and visualization and for the extraction of descriptive quantitative parameters of the vessel tree. The images and vessel parameters could serve as a basis for early diagnostics and classification of systemic inflammatory vascular diseases like vasculitis. Due to the non-invasiveness of the method, longitudinal studies in the course of treatment could be performed to monitor its success. (author)
DEFF Research Database (Denmark)
Gil-Cacho, Jose M.; van Waterschoot, Toon; Moonen, Marc;
2014-01-01
In this paper, we propose a new framework to tackle the double-talk (DT) problem in acoustic echo cancellation (AEC). It is based on a frequency-domain adaptive filter (FDAF) implementation of the so-called prediction error method adaptive filtering using row operations (PEM-AFROW) leading...... to the FDAF-PEM-AFROW algorithm. We show that FDAF-PEM-AFROW is by construction related to the best linear unbiased estimate (BLUE) of the echo path. We depart from this framework to show an improvement in performance with respect to other adaptive filters minimizing the BLUE criterion, namely the PEM...
Novel architecture for ultra-stable micro-ring resonator based optical frequency combs
Pasquazi, Alessia; Peccianti, Marco; Clerici, Matteo; Ferrera, Marcello; Razzari, Luca; Duchesne, David; Little, Brent E; Chu, Sai T; Moss, David J; Morandotti, Roberto
2014-01-01
We report a novel geometry for OPOs based on nonlinear microcavity resonators. This approach relies on a self-locked scheme that enables OPO emission without the need for thermal locking of the pump laser to the microcavity resonance. By exploiting a CMOS-compatible microring resonator, we achieve oscillation with a complete absence of shutting down, or self-terminating behavior, a very common occurrence in externally pumped OPOs. Further, this scheme consistently produces very wide bandwidth (>300nm, limited by our experimental set-up) combs that oscillate at a spacing of the FSR of the micro cavity resonance.
Wang, Yingjie; Liu, Haiyuan; HAN, XUELONG; Wang, Kangan
2015-01-01
With some of the intermittent new energy and large nonlinear loads, grid voltage unbalance, harmonics, and frequency deviation are increasing year by year. The voltage source converter (VSC) is seriously affected by the various unexpected factors, and the presence of grid impedance makes the situation worse. In order to make the VSC track the nonideal grid quickly and accurately, this paper proposes a frequency-adaptive grid-virtual-flux synchronization by multiple second-order generalized in...
Chek, MCH; Kwok, YK
2004-01-01
In contrast to traditional frequency hopping techniques, Adaptive Frequency Hopping (AFH) is a low cost and low power solution to avoid interference dynamically. While each AFH algorithm proposed previously is shown to be efficient, a detailed performance analysis of various AFH mechanisms under realistic resource constraints is yet to be done. In particular, based on our performance study on Bluetooth systems presented in this paper, we have found that the AFH mechanism adopted by IEEE 802.1...
Directory of Open Access Journals (Sweden)
Sridhar Krishnan
2007-07-01
Full Text Available This paper introduces a novel algorithm to excise single and multicomponent chirp-like interferences in direct sequence spread spectrum (DSSS communications. The excision algorithm consists of two stages: adaptive signal decomposition stage and directional element detection stage based on the Hough-Radon transform (HRT. Initially, the received spread spectrum signal is decomposed into its time-frequency (TF functions using an adaptive signal decomposition algorithm, and the resulting TF functions are mapped onto the TF plane. We then use a line detection algorithm based on the HRT that operates on the image of the TF plane and detects energy varying directional elements that satisfy a parametric constraint. Interference is modeled by reconstructing the corresponding TF functions detected by the HRT, and subtracted from the received signal. The proposed technique has two main advantages: (i it localizes the interferences on the TF plane with no cross-terms, thus facilitating simple filtering techniques based on thresholding of the TF functions, and is an efficient way to excise the interference; (ii it can be used for the detection of any directional interferences that can be parameterized. Simulation results with synthetic models have shown successful performance with linear and quadratic chirp interferences for single and multicomponent interference cases. The proposed method excises the interference even under very low SNR conditions of Ã¢ÂˆÂ’10Ã¢Â€Â‰dB, and the technique could be easily extended to any interferences that could be represented by a parametric equation in the TF plane.
Directory of Open Access Journals (Sweden)
Shaofei Xie
2012-02-01
Full Text Available Based on the theory of stochastic resonance, an adaptive single-well stochastic resonance (ASSR coupled with genetic algorithm was developed to enhance the signal-to-noise ratio of weak chromatographic signals. In conventional stochastic resonance algorithm, there are two or more parameters needed to be optimized and the proper parameters values were obtained by a universal searching within a given range. In the developed ASSR, the optimization of system parameter was simplified and automatic implemented. The ASSR was applied to the trace analysis of clenbuterol in human urine and it helped to significantly improve the limit of detection and limit of quantification of clenbuterol. Good linearity, precision and accuracy of the proposed method ensure that it could be an effective tool for trace analysis and the improvement of detective sensibility of current detectors.
Hirata, Akimasa; Yanase, Kazuya; Laakso, Ilkka; Chan, Kwok Hung; Fujiwara, Osamu; Nagaoka, Tomoaki; Watanabe, Soichi; Conil, Emmanuelle; Wiart, Joe
2012-12-21
According to the international guidelines, the whole-body averaged specific absorption rate (WBA-SAR) is used as a metric of basic restriction for radio-frequency whole-body exposure. It is well known that the WBA-SAR largely depends on the frequency of the incident wave for a given incident power density. The frequency at which the WBA-SAR becomes maximal is called the 'resonance frequency'. Our previous study proposed a scheme for estimating the WBA-SAR at this resonance frequency based on an analogy between the power absorption characteristic of human models in free space and that of a dipole antenna. However, a scheme for estimating the WBA-SAR in a grounded human has not been discussed sufficiently, even though the WBA-SAR in a grounded human is larger than that in an ungrounded human. In this study, with the use of the finite-difference time-domain method, the grounded condition is confirmed to be the worst-case exposure for human body models in a standing posture. Then, WBA-SARs in grounded human models are calculated at their respective resonant frequencies. A formula for estimating the WBA-SAR of a human standing on the ground is proposed based on an analogy with a quarter-wavelength monopole antenna. First, homogenized human body models are shown to provide the conservative WBA-SAR as compared with anatomically based models. Based on the formula proposed here, the WBA-SARs in grounded human models are approximately 10% larger than those in free space. The variability of the WBA-SAR was shown to be ±30% even for humans of the same age, which is caused by the body shape. PMID:23202273
A Dual-Bridge LLC Resonant Converter with Fixed-Frequency PWM Control for Wide Input Applications
DEFF Research Database (Denmark)
Xiaofeng, Sun; Li, Xiaohua; Shen, Yanfeng;
2017-01-01
. Compared with the traditional pulse frequency modulation (PFM) controlled HB/FB LLC resonant converter, the voltage gain range is independent of the quality factor and the magnetizing inductor has little influence on the voltage gain, which can simplify the parameter selection process and benefit...... the design of magnetic components as well. Over the full load range, zero voltage switching (ZVS) and zero current switching (ZCS) can be achieved for primary switches and secondary rectifier diodes, respectively. Detailed analysis on the modulation schedule and operating principle of the proposed converter......This paper proposes a dual-bridge (DB) LLC resonant converter for wide input applications. The topology is an integration of a half-bridge (HB) LLC circuit and a full-bridge (FB) LLC circuit. The fixed-frequency PWM control is employed and a range of twice the minimum input voltage can be covered...
Kim, Sangsik; Wang, Cong; Jaramillo-Villegas, Jose A; Xue, Xiaoxiao; Bao, Chengying; Xuan, Yi; Leaird, Daniel E; Weiner, Andrew M; Qi, Minghao
2016-01-01
Kerr nonlinearity based frequency combs and solitons have been generated from on-chip optical microresonators with high quality factors and global or local anomalous dispersion. However, fabrication of such resonators usually requires materials and/or processes that are not standard in semiconductor manufacturing facilities. Moreover, in certain frequency regimes such as visible and ultra-violet, the large normal material dispersion makes it extremely difficult to achieve anomalous dispersion. Here we present a concentric racetrack-shaped resonator that achieves anomalous dispersion in a 300 nm thick silicon nitride film, suitable for semiconductor manufacturing but previously thought to result only in waveguides with high normal dispersion, a high intrinsic Q of 1.5 million, and a novel mode-selective coupling scheme that allows coherent combs to be generated. We also provide evidence suggestive of soliton-like pulse formation in the generated comb. Our method can achieve anomalous dispersion over moderately...
Dong, Zheng-Gao; Liu, Hui; Li, Tao; Zhu, Zhi-Hong; Wang, Shu-Ming; Cao, Jing-Xiao; Zhu, Shi-Ning; Zhang, X
2008-12-01
We demonstrate that left-handed resonance transmission from metallic metamaterial, composed of periodically arranged double rings, can be extended to visible spectrum by introducing an active medium layer as the substrate. The severe ohmic loss inside metals at optical frequencies is compensated by stimulated emission of radiation in this active system. Due to the resonance amplification mechanism of recently proposed lasing spaser, the left-handed transmission band can be restored up to 610 nm wavelength, in dependence on the gain coefficient of the active layer. Additionally, threshold gains for different scaling levels of the double-ring unit are investigated to evaluate the gain requirement of left-handed transmission restoration at different frequency ranges.
Thermal self-frequency locking of doubly-resonant optical parametric oscillator
DEFF Research Database (Denmark)
Hansen, P.L.; Buchhave, Preben
1997-01-01
The increase in the circulating signal and idler fields that occurs in a high-Q doubly resonant optical parametric oscillator (OPO) as it approaches resonance results in a small increase in the crystal temperature owing to absorption of the generated fields. The temperature change affects...
Multi-frequency force-detected electron spin resonance in the millimeter-wave region up to 150 GHz
Ohmichi, E.; Tokuda, Y.; Tabuse, R.; Tsubokura, D.; Okamoto, T.; Ohta, H.
2016-07-01
In this article, a novel technique is developed for multi-frequency force-detected electron spin resonance (ESR) in the millimeter-wave region. We constructed a compact ESR probehead, in which the cantilever bending is sensitively detected by a fiber-optic Fabry-Perot interferometer. With this setup, ESR absorption of diphenyl-picrylhydrazyl radical (<1 μg) was clearly observed at multiple frequencies of up to 150 GHz. We also observed the hyperfine splitting of low-concentration Mn2+ impurities(˜0.2%) in MgO.
Nguyen, Thach G; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J
2015-01-01
We demonstrate a photonic RF Hilbert transformer for broadband microwave in-phase and quadrature-phase generation based on an integrated frequency optical comb, generated using a nonlinear microring resonator based on a CMOS compatible, high-index contrast, doped-silica glass platform. The high quality and large frequency spacing of the comb enables filters with up to 20 taps, allowing us to demonstrate a quadrature filter with more than a 5-octave (3 dB) bandwidth and an almost uniform phase response.
Lednická, M. (Markéta); Kaláb, Z. (Zdeněk)
2014-01-01
Resonant frequency and its changes in the surroundings of the permanent seismic station in the village of Stonava have been studied in this paper. Three different sets of seismic events were elaborated: local mining induced seismic events, distant earthquakes and seismic noise. Two data sets recorded at the permanent seismic station STO2 were used for spectral ratio computation using the HVSR method. First data set contains 20 records of mining induced seismic events with maximum epicental di...
Nonlinear magneto-optical rotation of frequency-modulated light resonant with a low-J transition
Malakyan, Y P; Budker, D; Kimball, D F; Yashchuk, V V; Malakyan, Yu. P.
2003-01-01
A low-light-power theory of nonlinear magneto-optical rotation of frequency-modulated light resonant with a J=1->J'=0 transition is presented. The theory is developed for a Doppler-free transition, and then modified to account for Doppler broadening and velocity mixing due to collisions. The results of the theory are shown to be in qualitative agreement with experimental data obtained for the rubidium D1 line.
Directory of Open Access Journals (Sweden)
P.Pradhan
2012-04-01
Full Text Available A new method of calculation of resonant frequencyof a rectangular patch antenna using Artificial NeuralNetwork (ANN has been adopted in this paper.ANN model has been developed and tested infrequency range of 1GHz to 3GHz to analyzeresonant frequency and slot length in rectangularMicrostrip Patch Antenna. The results obtained usingANN, are compared to the results obtained usingsoftware FEKO and experiment.
Frequency and Spatial Domains Adaptive-based Enhancement Technique for Thermal Infrared Images
Directory of Open Access Journals (Sweden)
Debasis Chaudhuri
2014-09-01
Full Text Available Low contrast and noisy image limits the amount of information conveyed to the user. With the proliferation of digital imagery and computer interface between man-and-machine, it is now viable to consider digital enhancement in the image before presenting it to the user, thus increasing the information throughput. With better contrast, target detection and discrimination can be improved. The paper presents a sequence of filtering operations in frequency and spatial domains to improve the quality of the thermal infrared (IR images. Basically, two filters – homomorphic filter followed by adaptive Gaussian filter are applied to improve the quality of the thermal IR images. We have systematically evaluated the algorithm on a variety of images and carefully compared it with the techniques presented in the literature. We performed an evaluation of three filter banks such as homomorphic, Gaussian 5×5 and the proposed method, and we have seen that the proposed method yields optimal PSNR for all the thermal images. The results demonstrate that the proposed algorithm is efficient for enhancement of thermal IR images.Defence Science Journal, Vol. 64, No. 5, September 2014, pp.451-457, DOI:http://dx.doi.org/10.14429/dsj.64.6873
Mitchell, D A; Sault, R J
2010-01-01
In radio astronomy, reference signals from auxiliary antennas that receive only the radio frequency interference (RFI) can be modified to model the RFI environment at the astronomy receivers. The RFI can then be canceled from the astronomy signal paths. However, astronomers typically only require signal statistics. If the RFI statistics are changing slowly, the cancellation can be applied to the signal correlations at a much lower rate than is required for standard adaptive filters. In this paper we describe five canceler setups; precorrelation and postcorrelation cancelers that use one or two reference signals in different ways. The theoretical residual RFI and added noise levels are examined and are demonstrated using microwave television RFI at the Australia Telescope Compact Array. The RFI is attenuated to below the system noise, a reduction of at least 20 dB. While dual-reference cancelers add more reference noise than single-reference cancelers, this noise is zero-mean and only adds to the system noise,...
Peña, M.
2016-10-01
Achieving acceptable signal-to-noise ratio (SNR) can be difficult when working in sparsely populated waters and/or when species have low scattering such as fluid filled animals. The increasing use of higher frequencies and the study of deeper depths in fisheries acoustics, as well as the use of commercial vessels, is raising the need to employ good denoising algorithms. The use of a lower Sv threshold to remove noise or unwanted targets is not suitable in many cases and increases the relative background noise component in the echogram, demanding more effectiveness from denoising algorithms. The Adaptive Wiener Filter (AWF) denoising algorithm is presented in this study. The technique is based on the AWF commonly used in digital photography and video enhancement. The algorithm firstly increments the quality of the data with a variance-dependent smoothing, before estimating the noise level as the envelope of the Sv minima. The AWF denoising algorithm outperforms existing algorithms in the presence of gaussian, speckle and salt & pepper noise, although impulse noise needs to be previously removed. Cleaned echograms present homogenous echotraces with outlined edges.
Energy Technology Data Exchange (ETDEWEB)
Olsrud, Johan; Wirestam, Ronnie; Brockstedt, Sara; Persson, Bertil R.R. [Department of Radiation Physics, Lund University Hospital, SE-221 85 Lund (Sweden); Nilsson, Annika M.K. [Department of Physics, Lund Institute of Technology, SE-221 00 Lund (Sweden); Tranberg, Karl-Goeran [Department of Surgery, Lund University Hospital, SE-221 85 Lund (Sweden); Staahlberg, Freddy [Department of Radiation Physics, Lund University Hospital, SE-221 85 Lund (Sweden); Department of Diagnostic Radiology, Lund University Hospital, SE-221 85 Lund (Sweden)
1998-09-01
In this work the temperature dependence of the proton resonance frequency was assessed in agarose gel with a high melting temperature (95 deg. C) and in porcine liver in vitro at temperatures relevant to thermotherapy (25-80 deg. C). Furthermore, an optically tissue-like agarose gel phantom was developed and evaluated for use in MRI. The phantom was used to visualize temperature distributions from a diffusing laser fibre by means of the proton resonance frequency shift method. An approximately linear relationship (0.0085 ppm deg. C{sup -1}) between proton resonance frequency shift and temperature change was found for agarose gel, whereas deviations from a linear relationship were observed for porcine liver. The optically tissue-like agarose gel allowed reliable MRI temperature monitoring, and the MR relaxation times (T{sub 1} and T{sub 2}) and the optical properties were found to be independently alterable. Temperature distributions around a diffusing laser fibre, during irradiation and subsequent cooling, were assessed with high spatial resolution (voxel size = 4.3 mm{sup 3}) and with random uncertainties ranging from 0.3 deg. C to 1.4 deg. C (1 SD) with a 40 s scan time. (author)
Directory of Open Access Journals (Sweden)
Zhu Yi-Sheng
2003-01-01
Full Text Available An adaptive hierarchical lapped orthogonal transform (HLOT exciser is proposed for tracking, localizing, and rejecting the nonstationary interference in direct sequence spread spectrum (DSSS communications. The method is based on HLOT. It utilizes a fast dynamic programming algorithm to search for the best basis, which matches the interference structure best, in a library of lapped orthogonal bases. The adaptive HLOT differs from conventional block transform and the more advanced modulated lapped transform (MLT in that the former produces arbitrary time-frequency tiling, which can be adapted to the signal structure, while the latter yields fixed tilings. The time-frequency tiling of the adaptive HLOT can be time varying, so it is also able to track the variations of the signal time-frequency structure. Simulation results show that the proposed exciser brings significant performance improvement in the presence of nonstationary time-localized interference with or without instantaneous frequency (IF information compared with the existing block transform domain excisers. Also, the proposed exciser is effective in suppressing narrowband interference and combined narrowband and time-localized impulsive interference.
Egalisation adaptative et non invasive de la reponse temps-frequence d'une petite salle
Martin, Tristan
frequency bands, the filter response arising from the inversion of the room/speaker frequency response. The resulting dynamically adapting filter has properties similar to those of the human ear, a significant spectral-resolution in lower frequencies, and high time-resolution at high frequencies. The response corrected by the filter system tends approaching to a pure pulse. Techniques explored in the context of this research led to the publication of a scientific article in a peer reviewed journal and one conference paper in which similar methods were used for mining engineering applications. (Abstract shortened by UMI.).
225-255-GHz InP DHBT Frequency Tripler MMIC Using Complementary Split-Ring Resonator
Li, Xiao; Zhang, Yong; Li, Oupeng; Sun, Yan; Lu, Haiyan; Cheng, Wei; Xu, Ruimin
2016-10-01
In this paper, a novel design of frequency tripler monolithic microwave integrated circuit (MMIC) using complementary split-ring resonator (CSRR) is proposed based on 0.5-μm InP DHBT process. The CSRR-loaded microstrip structure is integrated in the tripler as a part of impedance matching network to suppress the fundamental harmonic, and another frequency tripler based on conventional band-pass filter is presented for comparison. The frequency tripler based on CSRR-loaded microstrip generates an output power between -8 and -4 dBm from 228 to 255 GHz when the input power is 6 dBm. The suppression of fundamental harmonic is better than 20 dBc at 77-82 GHz input frequency within only 0.15 × 0.15 mm2 chip area of the CSRR structure on the ground layer. Compared with the frequency tripler based on band-pass filter, the tripler using CSRR-loaded microstrip obtains a similar suppression level of unwanted harmonics and higher conversion gain within a much smaller chip area. To our best knowledge, it is the first time that CSRR is used for harmonic suppression of frequency multiplier at such high frequency band.
International Nuclear Information System (INIS)
In the theory of resonant mode coupling, the parent and child modes are directly related in frequency and phase. The oscillations present in the fast rotating δ Sct star KIC 8054146 allow us to test the most general and generic aspects of such a theory. The only direct way to separate the parent and coupled (child) modes is to examine the correlations in amplitude variability between the different frequencies. For the dominant family of related frequencies, only a single mode and a triplet are the origins of nine dominant frequency peaks ranging from 2.93 to 66.30 cycles day–1 (as well as dozens of small-amplitude combination modes and a predicted and detected third high-frequency triplet). The mode-coupling model correctly predicts the large amplitude variations of the coupled modes as a product of the amplitudes of the parent modes, while the phase changes are also correctly modeled. This differs from the behavior of 'normal' combination frequencies in that the amplitudes are three orders of magnitude larger and may exceed even the amplitudes of the parent modes. We show that two dominant low frequencies at 5.86 and 2.93 cycles day–1 in the gravity-mode region are not harmonics of each other, and their properties follow those of the almost equidistant high-frequency triplet. We note that the previously puzzling situation of finding two strong peaks in the low-frequency region related by nearly a factor of two in frequency has been seen in other δ Sct stars as well.
Energy Technology Data Exchange (ETDEWEB)
Breger, M.; Montgomery, M. H. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States)
2014-03-10
In the theory of resonant mode coupling, the parent and child modes are directly related in frequency and phase. The oscillations present in the fast rotating δ Sct star KIC 8054146 allow us to test the most general and generic aspects of such a theory. The only direct way to separate the parent and coupled (child) modes is to examine the correlations in amplitude variability between the different frequencies. For the dominant family of related frequencies, only a single mode and a triplet are the origins of nine dominant frequency peaks ranging from 2.93 to 66.30 cycles day{sup –1} (as well as dozens of small-amplitude combination modes and a predicted and detected third high-frequency triplet). The mode-coupling model correctly predicts the large amplitude variations of the coupled modes as a product of the amplitudes of the parent modes, while the phase changes are also correctly modeled. This differs from the behavior of 'normal' combination frequencies in that the amplitudes are three orders of magnitude larger and may exceed even the amplitudes of the parent modes. We show that two dominant low frequencies at 5.86 and 2.93 cycles day{sup –1} in the gravity-mode region are not harmonics of each other, and their properties follow those of the almost equidistant high-frequency triplet. We note that the previously puzzling situation of finding two strong peaks in the low-frequency region related by nearly a factor of two in frequency has been seen in other δ Sct stars as well.
Breger, M.; Montgomery, M. H.
2014-03-01
In the theory of resonant mode coupling, the parent and child modes are directly related in frequency and phase. The oscillations present in the fast rotating δ Sct star KIC 8054146 allow us to test the most general and generic aspects of such a theory. The only direct way to separate the parent and coupled (child) modes is to examine the correlations in amplitude variability between the different frequencies. For the dominant family of related frequencies, only a single mode and a triplet are the origins of nine dominant frequency peaks ranging from 2.93 to 66.30 cycles day-1 (as well as dozens of small-amplitude combination modes and a predicted and detected third high-frequency triplet). The mode-coupling model correctly predicts the large amplitude variations of the coupled modes as a product of the amplitudes of the parent modes, while the phase changes are also correctly modeled. This differs from the behavior of "normal" combination frequencies in that the amplitudes are three orders of magnitude larger and may exceed even the amplitudes of the parent modes. We show that two dominant low frequencies at 5.86 and 2.93 cycles day-1 in the gravity-mode region are not harmonics of each other, and their properties follow those of the almost equidistant high-frequency triplet. We note that the previously puzzling situation of finding two strong peaks in the low-frequency region related by nearly a factor of two in frequency has been seen in other δ Sct stars as well.
Lucas del Pozo, Irene; Michelena, M D; de Manuel, V; Duch, M; Esteve, J; Plaza, J A
2010-01-01
The dynamic properties of membranes have been object of many researches since they can be used as sensor heads in different devices. Some methods have been proposed to solve the problem of determining the resonance frequencies and their dependence on the stress caused by forces applied on the membrane surface. The problem of the vibrating rectangular membrane under a stress caused by a uniform in-plane force is well known. However, the resonance frequency behaviour when the force is out-of-plane instead of in-plane, is not so well understood and documented. A gradiometer which uses a silicon square membrane with a magnet fixed on it as a sensor head has been developed in a previous work. This device reports a quadratic dependence of the frequency on the out-of-plane magnetic force. In this work, simulations to obtain the dependence of the frequency of the fundamental flexural mode on the stress have been performed. It has been studied the influence of in-plane and out-of-plane forces applied to the membrane. ...
Lin, Jiao; Huang, Lujun; Yu, Yiling; He, Sailing; Cao, Linyou
2015-07-27
We present an approach of deterministic phase engineering that can enable the rational design of optical Fano resonances with arbitrarily pre-specified lineshapes. Unlike all the approaches previously used to design optical Fano resonances, which fall short of designing the resonances with arbitrary lineshapes because of the lack of information for the optical phases involved, we develop our approach by capitalizing on unambiguous knowledge for the phase of optical modes. Optical Fano resonances arise from the interference of photons interacting with two optical modes with substantially different quality factors. We find that the phase difference of the two modes involved in optical Fano resonances is determined by the eigenfrequency difference of the modes. This allows us to deterministically engineer the phase by tuning the eigenfrequency, which may be very straightforward. We use dielectric grating structures as an example to illustrate the notion of deterministic engineering for the design of optical Fano resonances with arbitrarily pre-specified symmetry, linewidth, and wavelengths. PMID:26367578
Bouchaala, Adam M.
2016-03-18
We present analytical formulations to calculate the induced resonance frequency shifts of electrically actuated clamped–clamped micro and nano (Carbon nanotube) beams due to an added mass. Based on the Euler–Bernoulli beam theory, we investigate the linear dynamic responses of the beams added masses, which are modeled as discrete point masses. Analytical expressions based on perturbation techniques and a one-mode Galerkin approximation are developed to calculate accurately the frequency shifts under a DC voltage as a function of the added mass and position. The analytical results are compared to numerical solution of the eigenvalue problem. Results are shown for the fundamental as well as the higher-order modes of the beams. The results indicate a significant increase in the frequency shift, and hence the sensitivity of detection, when scaling down to nano scale and using higher-order modes. © 2016 Springer Science+Business Media Dordrecht
Phuoc, Nguyen N.; Ong, C. K.
2016-06-01
We report our detailed investigation of the electrical tuning of the ferromagnetic resonance frequency and frequency linewidth in multiferroic heterostructures consisting of FeCo thin films grown onto [Pb(Mg1/3Nb2/3) O3]0.68-[PbTiO3]0.32 (PMN-PT) substrates with NiFe underlayers. Our study shows that the electrical tuning range of both ferromagnetic resonance frequency and frequency linewidth in this FeCo/PMN-PT heterostructure can be very large. Specifically, the resonance frequency can be tuned from 1.8 GHz to 10.3 GHz, and the frequency linewidth can be changed from 1.6 GHz to 7.3 GHz. The electrical tuning of these microwave properties is discussed in conjunction with the result from the static magnetic characterization and is explained based on the strain-driven magnetoelectric heterostructured effect.
Vidigal, P G; Dittmer, S; Steinmann, E; Buer, J; Rath, P-M; Steinmann, J
2014-07-01
Due to the continuous exposure to a challenging environment and repeated antibiotic treatment courses, bacterial populations in cystic fibrosis (CF) patients experience selective pressure causing the emergence of mutator phenotypes. In this study we investigated the genotypic diversity, mutation frequency and antibiotic resistance of S. maltophilia isolates chronically colonizing CF patients. S. maltophilia was isolated from a total of 90 sputum samples, collected sequentially from 19 CF patients admitted between January 2008 and March 2012 at the University Hospital Essen, Germany. DNA fingerprinting by repetitive-sequence-based PCR revealed that 68.4% (n=13) of CF patients harbored different S. maltophilia genotypes during the 4-year study course. Out of 90 S. maltophilia isolates obtained from chronically colonized CF patients, 17.8% (n=16) were hypomutators, 27.7% (n=25), normomutators, 23.3% (n=21), weak hypermutators and 31.2% (n=28) strong hypermutators. We also found that mutation rates of the most clonally related genotypes varied over time with the tendency to become less mutable. Mutator isolates were found to have no significant increase in resistance against eight different antibiotics versus nonmutators. Sequencing of the mismatch repair genes mutL, mutS and uvrD revealed alterations that resulted in amino acid changes in their corresponding proteins. Here, we could demonstrate that several different S. maltophilia genotypes are present in CF patients and as a sign of adaption their mutation status switches over time to a less mutator phenotype without increasing resistance. These results suggest that S. maltophilia attempts to sustain its biological fitness as mechanism for long-term persistence in the CF lung. PMID:24836944
Breger, Michel
2014-01-01
In the theory of resonant mode coupling, the parent and child modes are directly related in frequency and phase. The oscillations present in the fast rotating Delta Scuti star KIC 8054146 allow us to test the most general and generic aspects of such a theory. The only direct way to separate the parent and coupled (child) modes is to examine the correlations in amplitude variability between the different frequencies. For the dominant family of related frequencies, only a single mode and a triplet are the origins of nine dominant frequency peaks ranging from 2.93 to 66.30 cycles per day (as well as dozens of small-amplitude combination modes and a predicted and detected third high-frequency triplet). The mode-coupling model correctly predicts the large amplitude variations of the coupled modes as a product of the amplitudes of the parent modes, while the phase changes are also correctly modeled. This differs from the behavior of 'normal' combination frequencies in that the amplitudes are three orders of magnitu...
Koelsch, Patrick; Muglali, Mutlu; Rohwerder, Michael; Erbe, Andreas
2013-01-01
Vibrational sum-frequency-generation (SFG) spectroscopy experiments at electrified interfaces involve incident laser radiation at frequencies in the IR and near-IR/visible regions as well as a static electric field on the surface. Here we show that mixing the three fields present on the surface can result in third-order effects in resonant SFG signals. This was achieved for closed packed self-assembled monolayers (SAMs) with molecular groups of high optical nonlinearity and surface potentials similar to those typically applied in cyclic voltammograms. Broadband SFG spectroscopy was applied to study a hydrophobic well-ordered araliphatic SAM on a Au(111) surface using a thin-layer analysis cell for spectro-electrochemical investigations in a 100 mM NaOH electrolyte solution. Resonant contributions were experimentally separated from non-resonant contributions of the Au substrate and theoretically analyzed using a fitting function including third-order terms. The resulting ratio of third-order to second-order susceptibilities was estimated to be [Formula: see text](10(-10)) m/V. PMID:24235781
Directory of Open Access Journals (Sweden)
Lei Zhao
2015-04-01
Full Text Available In this paper, a load adaptive control method to improve the efficiency and dynamic performance of the Phase-Shifted Full-Bridge (PSFB converter which works under a wide range of load conditions is presented. The proposed control method can be used as a battery charger since this application demands a wide range of load conditions. The composition of the PSFB converter’s losses and the loss analysis model are both discussed. According to this model, the optimum switching frequency which results in minimum power loss is adopted to improve the efficiency. The relationship between switching frequency and power loss is formulated over a wide load range. Indicated by this kind of relationship, the proposed controller adjusts the switching frequency at different load currents. Moreover, an adaptive gain adjustment controller is applied to replace the traditional controller, with the aim to improve the dynamic performance which is influenced by the changes of the switching frequency and load current. In addition, the experimental results show that the maximum improvement of efficiency is up to 20%. These results confirm the effectiveness of the proposed load adaptive control method.
Symmetric and Asymmetric Split Ring Resonators for Biosensing at Terahertz Frequencies
Naranjo, Guillermo; Peralta, Xomalin
2015-03-01
Food allergies have become a major health concern around the world. Peanut allergies are particularly important because they affect over 5 million people in the United States. We are proposing to develop a metamaterial-based sensor for peanut allergens. The detection mechanism we will tap into is the change in a metamaterial's resonant response due to the presence of a biomolecule in the gap region. Using a commercial-grade simulator based on the finite-difference time-domain method, we have simulated the terahertz transmission and reflection spectra of three different split-ring resonator designs with and without a biomolecule present. By modifying the overall symmetry of the resonator and the geometry of the gap region, we have modified the resonant response and increased its sensitivity. The increased sensitivity is demonstrated by repeating the simulations with a layer of peroxidase conjugated immunoglobulin G (PX-IgG) in the gap region and quantifying the resulting resonant shift. These results are the basis for the proposed allergen sensors. UTSA MBRS-RISE Research Training Program.
Singly-resonant sum frequency generation of visible light in a semiconductor disk laser
Andersen, Martin Thalbitzer; Schlosser, P.J.; J. E. Hastie; Tidemand-Lichtenberg, Peter; Dawson, M.D.; Pedersen, Christian
2009-01-01
In this paper a generic approach for visible light generation is presented. It is based on sum frequency generation between a semiconductor disk laser and a solid-state laser, where the frequency mixing is achieved within the cavity of the semiconductor disk laser using a singlepass of the solid-state laser light. This exploits the good beam quality and high intra-cavity power present in the semiconductor disk laser to achieve high conversion efficiency. Combining sum frequency mixing and sem...
Effects of pulse frequency modulation on three-step resonance laser ionization
International Nuclear Information System (INIS)
Through numerical solution of the Schroedinger equation the authors illustrate the effects of frequency modulation laser upon the excitation of a four-level system irradiated by simultaneous laser pulse. When the laser power is sufficiently great and the frequency modulation parameters are suitable, it shows that the frequency modulation excitation applied to a Gaussin statistical distribution of detunings can obtain more effective three-step photoionization than monochromatic or amplitude modulation excitation does
Resonances and superlattice pattern stabilization in two-frequency forced Faraday waves
Topaz, Chad M.; Silber, Mary
2001-01-01
We investigate the role weakly damped modes play in the selection of Faraday wave patterns forced with rationally-related frequency components m*omega and n*omega. We use symmetry considerations to argue for the special importance of the weakly damped modes oscillating with twice the frequency of the critical mode, and those oscillating primarily with the "difference frequency" |n-m|*omega and the "sum frequency" (n+m)*omega. We then perform a weakly nonlinear analysis using equations of Zhan...
Resonance frequency shifts due to quantized electronic states in atomically thin NEMS
Chen, Changyao; Deshpande, Vikram; Koshino, Mikito; Lee, Sunwoo; Gondarenko, Alexander; MacDonald, Allan; Kim, Philip; Hone, James
The classic picture of the force exerted on a parallel plate capacitor assumes infinite density of states (DOS), which implies identical electrochemical and electrostatic potential. However, such assumption can breakdown in low-dimensional devices where the DOS is finite or quantized. Here we consider the mechanical resonance shift of a nanoelectromechanical (NEMS) resonator with small DOS, actuated and detected capacitively at fixed electrochemical potential. We found three leading correction terms to the classical picture: the first term leads to the modulation of static force due to the variation in chemical potential, and the second and third terms are related to the static and dynamic changes in spring constants, caused by quantum capacitance. The theory agrees well with recent experimental findings from graphene resonator in quantum Hall regimes, where the chemical potential and quantum capacitance are tuned by magnetic field, while the gate voltage is kept constant.
Institute of Scientific and Technical Information of China (English)
HONG Ling-Fei; ZHANG Chun-Xi; FENG Li-Shuang; YU Huai-Yong; LEI Ming
2012-01-01
Resonator micro-optic gyro (R-MOG) sensing rotation angular-velocity is based on Sagnac effect.We present a frequency modulation (FM) induced by the analog triangle-waveform phase modulation (ATAW-PM) technique in an R-MOG.Compared with the traditional serrodyne phase modulation or digital phase modulation methods,the proposed modulation technique has the intrinsic advantage in free of sweeping-back or step-effect induced pulse noise.The influence on dynamic range and resolution of the R-MOG by the parameters of analog trianglewaveform is theoretically analyzed.Experiments are carried out on an R-MOG composed of an integrated optic resonator with a free spectral range (FSR) and a fitness (F) of 1.6GHz and 61,respectively.Dynamic range of ±500 deg/s and bias drift of 0.6 deg/s over 1 h and 0.05 deg/s for 60 s are reliably obtained.%Resonator micro-optic gyro (R-MOG) sensing rotation angular-velocity is based on Sagnac effect. We present a frequency modulation (FM) induced by the analog triangle-waveform phase modulation (ATAW-PM) technique in an R-MOG. Compared with the traditional serrodyne phase modulation or digital phase modulation methods, the proposed modulation technique has the intrinsic advantage in free of sweeping-back or step-effect induced pulse noise. The influence on dynamic range and resolution of the R-MOG by the parameters of analog triangle-waveform is theoretically analyzed. Experiments are carried out on an R-MOG composed of an integrated optic resonator with a free spectral range (FSR) and a Btness (F) of 1.6 GHz and 61, respectively. Dynamic range of ±500 deg/s and bias drift of 0.6deg/s over 1 h and 0.05deg/s for 60s are reliably obtained.
Singly-resonant sum frequency generation of visible light in a semiconductor disk laser
DEFF Research Database (Denmark)
Andersen, Martin Thalbitzer; Schlosser, P.J.; Hastie, J.E.;
2009-01-01
In this paper a generic approach for visible light generation is presented. It is based on sum frequency generation between a semiconductor disk laser and a solid-state laser, where the frequency mixing is achieved within the cavity of the semiconductor disk laser using a singlepass of the solid-...... spectrum, by appropriate choice of semiconductor material and single-pass laser wavelength.......In this paper a generic approach for visible light generation is presented. It is based on sum frequency generation between a semiconductor disk laser and a solid-state laser, where the frequency mixing is achieved within the cavity of the semiconductor disk laser using a singlepass of the solid......-state laser light. This exploits the good beam quality and high intra-cavity power present in the semiconductor disk laser to achieve high conversion efficiency. Combining sum frequency mixing and semiconductor disk lasers in this manner allows in principle for generation of any wavelength within the visible...
Decoupling crossover in asymmetric broadside coupled split-ring resonators at terahertz frequencies
DEFF Research Database (Denmark)
Keiser, G. R.; Strikwerda, Andrew; Fan, K.;
2013-01-01
comprising a coupled unit. We characterize the response of ABC-SRRs both numerically and experimentally via terahertz time-domain spectroscopy. As with symmetric BC-SRRs (Δg=0 μm), a large redshift in the LC resonance is observed with increasing displacement, resulting from changes in the capacitive...
The Effect of Electronic Paramagnetism on Nuclear Magnetic Resonance Frequencies in Metals
Townes, C. H.; Herring, C.; Knight, W. D.
1950-09-22
Observations on the shifts of nuclear resonances in metals ( Li{sup 7}, Na{sup 23}, Cu {sup 63}, Be{sup 9}, Pb{sup 207}, Al{sup 27}, and Ca{sup 69} ) due to free electron paramagnetism; comparison with theoretical values.
DEFF Research Database (Denmark)
Iwaszczuk, Krzysztof; Bisgaard, Christer Zoffmann; Andronico, Alessio;
2013-01-01
this symmetry by modification of the dielectric environment of the resonator, and demonstrate a fabrication-optimized structure based on a concentric grating design which efficiently couples the emitted radiation into a narrow, near-gaussian forward-propagating cone of well-defined linear or circular...
Vibration-induced displacement using high-frequency resonators and friction layers
DEFF Research Database (Denmark)
Thomsen, Jon Juel
1998-01-01
A mathematical model is set up to quantify vibration-induced motions of a slider with an imbedded resonator. A simple approximate expression is presented for predicting average velocities of the slider, agreeing fairly well with numerical integration of the full equations of motion. The simple ex...
Radio-frequency magnetic susceptibility of spin ice crystals Dy2Ti2O7 using tunnel diode resonator
Teknowijoyo, Serafim; Cho, Kyuil; Tanatar, Makariy A.; Prozorov, Ruslan; Cava, Robert J.; Krizan, Jason W.; Ames Laboratory; Iowa State University Team; Princeton University Collaboration
Spin ice compound, Dy2Ti2O7, has shown complex frequency - dependent magnetic behavior at low temperatures. While the DC measurements show conventional paramagnetic behavior, finite frequency susceptibility shows two regimes, - complex kagomé ice behavior at around 2 K and spin collective behavior above 10 K, depending on the frequency. Conventional AC susceptometry is limited to frequencies in a kHz range, but to get an insight into the possible Arrhenius activated behavior and characteristic relaxation times, higher frequencies are desired. We used self-oscillating tunnel-diode resonator (TDR) to probe magnetic susceptibility at 14.6 MHz, in the presence of a DC magnetic field and down to 50 mK. We found an unusual non-monotonic field dependence of the lower transition temperature, most likely associated with different spin configurations in a kagomé ice and an activated behavior of the upper transition, which has now shifted to 50 K range. This work was supported by the U.S. DOE BES MSED and was performed at the Ames Laboratory, Iowa State University under Contract DE-AC02-07CH11358. The work at Princeton university was supported by DOE BES Grant Number DE-FG02-08ER46544.
Xie, Huijuan; Gong, Yubing; Wang, Qi
2016-06-01
In this paper, we numerically study how time delay induces multiple coherence resonance (MCR) and synchronization transitions (ST) in adaptive Hodgkin-Huxley neuronal networks with spike-timing dependent plasticity (STDP). It is found that MCR induced by time delay STDP can be either enhanced or suppressed as the adjusting rate Ap of STDP changes, and ST by time delay varies with the increase of Ap, and there is optimal Ap by which the ST becomes strongest. It is also found that there are optimal network randomness and network size by which ST by time delay becomes strongest, and when Ap increases, the optimal network randomness and optimal network size increase and related ST is enhanced. These results show that STDP can either enhance or suppress MCR and optimal STDP can enhance ST induced by time delay in the adaptive neuronal networks. These findings provide a new insight into STDP's role for the information processing and transmission in neural systems.
Mahmood, Muhammad Tariq; Chu, Yeon-Ho; Choi, Young-Kyu
2016-06-01
This paper proposes a Rician noise reduction method for magnetic resonance (MR) images. The proposed method is based on adaptive non-local mean and guided image filtering techniques. In the first phase, a guidance image is obtained from the noisy image through an adaptive non-local mean filter. Sobel operators are applied to compute the strength of edges which is further used to control the spread of the kernel in non-local mean filtering. In the second phase, the noisy and the guidance images are provided to the guided image filter as input to restore the noise-free image. The improved performance of the proposed method is investigated using the simulated and real data sets of MR images. Its performance is also compared with the previously proposed state-of-the art methods. Comparative analysis demonstrates the superiority of the proposed scheme over the existing approaches.
International Nuclear Information System (INIS)
The influence of crystal defects on the phonon spectra was studied for fcc lead using superconducting tunneling spectroscopy. The theory predicts low frequency modes for the vibrational states of interstitials in (100) dumbbell configuration. Low temperature irradiation of superconducting point contacts with fast ions (point contact thickness small compared to the average ion range) showed radiation-induced structures in the low-energy part of the Eliashberg function for lead. These resonant modes are reduced by annealing at 18.5 K; they are attributed to small interstitial clusters. The radiation-induced structures are completely removed by room temperature annealing. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Klofai, Yerima [Department of Physics, Higher Teacher Training College, University of Maroua, PO Box 46 Maroua (Cameroon); Essimbi, B Z [Department of Physics, Faculty of Science, University of Yaounde 1, PO Box 812 Yaounde (Cameroon); Jaeger, D, E-mail: bessimb@yahoo.fr [ZHO, Optoelectronik, Universitaet Duisburg-Essen, D-47048 Duisburg (Germany)
2011-10-15
Pulse propagation on high-frequency dissipative nonlinear transmission lines (NLTLs)/resonant tunneling diode line cascaded maps is investigated for long-distance propagation of short pulses. Applying perturbative analysis, we show that the dynamics of each line is reduced to an expanded Korteweg-de Vries-Burgers equation. Moreover, it is found by computer experiments that the soliton developed in NLTLs experiences an exponential amplitude decay on the one hand and an exponential amplitude growth on the other. As a result, the behavior of a pulse in special electrical networks made of concatenated pieces of lines is closely similar to the transmission of information in optical/electrical communication systems.
International Nuclear Information System (INIS)
Pulse propagation on high-frequency dissipative nonlinear transmission lines (NLTLs)/resonant tunneling diode line cascaded maps is investigated for long-distance propagation of short pulses. Applying perturbative analysis, we show that the dynamics of each line is reduced to an expanded Korteweg-de Vries-Burgers equation. Moreover, it is found by computer experiments that the soliton developed in NLTLs experiences an exponential amplitude decay on the one hand and an exponential amplitude growth on the other. As a result, the behavior of a pulse in special electrical networks made of concatenated pieces of lines is closely similar to the transmission of information in optical/electrical communication systems.
Institute of Scientific and Technical Information of China (English)
YongjiYu; Guangyong Jin; Chao Wang; Xinyu Chen; Jiaxi Guo; Yibo Wang
2009-01-01
@@ A high power continuous-wave deep blue laser at 447 nm is obtained by using a doubly cavity and a type Π critical phase matching KTP crystal for intracavity sum-frequency-mixing.With the incident pump power of 240 W for the Nd:YAP crystal and 120 W for the other Nd:YAP crystal, the deep blue laser output of 5.7 W at 447 nm with near fundamental mode is obtained, and the beam quality M2 value equals 2.53 in both horizontal and vertical directions at the maximum output power.The power stability is better than 2% at the maximum output power during half an hour.The experimental results show that the intracavity sum-frequency mixing by doubly resonant is an effective method for high power blue laser.
Directory of Open Access Journals (Sweden)
V. C. Roldugin
Full Text Available The variations of the first mode of Schumann resonance are analyzed using data from Kola peninsula stations during the solar proton event of 6 November 1997. On this day the intensive flux of energetic protons on GOES-8 and the 10% increase of the count rate of the neutron monitor in Apatity between 1220 and 2000 UT were preceded by a solar X-ray burst at 1155 UT. This burst was accompanied by a simultaneous increase of the Schumann frequency by 3.5%, and the relativistic proton flux increase was accompanied by 1% frequency decrease. These effects are explained by changes of the height and dielectric permeability of the Earth-ionosphere cavity.
Key words. Ionosphere (ionospheric disturbances; solar radiation and cosmic ray effects · Radio science (ionospheric propagation
Yang, Yong; Kasumie, Sho; Zhao, Guangming; Xu, Linhua; Ward, Jonathan; Yang, Lan; Chormaic, Síle Nic
2016-01-01
Frequency comb generation in microresonators at visible wavelengths has found applications in a variety of areas such as metrology, sensing, and imaging. To achieve Kerr combs based on four-wave mixing in a microresonator, dispersion must be in the anomalous regime. In this work, we demonstrate dispersion engineering in a microbubble resonator (MBR) fabricated by a two-CO$_2$ laser beam technique. By decreasing the wall thickness of the MBR down to 1.4 $\\mu$m, the zero dispersion wavelength shifts to values shorter than 764 nm, making phase matching possible around 765 nm. With the optical \\textit{Q}-factor of the MBR modes being greater than $10^7$, four-wave mixing is observed at 765 nm for a pump power of 3 mW. By increasing the pump power, parametric oscillation is achieved, and a frequency comb with 14 comb lines is generated at visible wavelengths.
Sensitivity of spin-torque diodes for frequency-tunable resonant microwave detection
Wang, C.; Cui, Y.-T.; Sun, J. Z.; Katine, J. A.; Buhrman, R. A.; Ralph, D. C.
2009-09-01
We calculate the efficiency with which magnetic tunnel junctions can be used as resonant detectors of incident microwave radiation via the spin-torque diode effect. The expression we derive is in good agreement with the sensitivities we measure for MgO-based magnetic tunnel junctions with an extended (unpatterned) magnetic pinned layer. However, the measured sensitivities are reduced below our estimate for a second set of devices in which the pinned layer is a patterned synthetic antiferromagnet (SAF). We suggest that this reduction may be due to an undesirable coupling between the magnetic free layer and one of the magnetic layers within the etched SAF. Our calculations suggest that optimized tunnel junctions should achieve sensitivities for resonant detection exceeding 10 000 mV/mW.
Transient Schr\\"odinger-Poisson Simulations of a High-Frequency Resonant Tunneling Diode Oscillator
Mennemann, Jan-Frederik; Kosina, Hans
2012-01-01
Transient simulations of a resonant tunneling diode oscillator are presented. The semiconductor model for the diode consists of a set of time-dependent Schr\\"odinger equations coupled to the Poisson equation for the electric potential. The one-dimensional Schr\\"odinger equations are discretized by the finite-difference Crank-Nicolson scheme using memory-type transparent boundary conditions which model the injection of electrons from the reservoirs. This scheme is unconditionally stable and reflection-free at the boundary. An efficient recursive algorithm due to Arnold, Ehrhardt, and Sofronov is used to implement the transparent boundary conditions, enabling simulations which involve a very large number of time steps. Special care has been taken to provide a discretization of the boundary data which is completely compatible with the underlying finite-difference scheme. The transient regime between two stationary states and the self-oscillatory behavior of an oscillator circuit, containing a resonant tunneling ...
Feng, Y.; Clayton, E. H.; Chang, Y.; Okamoto, R.J.; Bayly, P.V.
2013-01-01
Characterization of the dynamic mechanical behavior of brain tissue is essential for understanding and simulating the mechanisms of traumatic brain injury (TBI). Changes in mechanical properties may also reflect changes in the brain due to aging or disease. In this study, we used magnetic resonance elastography (MRE) to measure the viscoelastic properties of ferret brain tissue in vivo. Three-dimensional (3D) displacement fields were acquired during wave propagation in the brain induced by ha...
Detailing Radio Frequency Heating Induced by Coronary Stents: A 7.0 Tesla Magnetic Resonance Study
Davide Santoro; Lukas Winter; Alexander Müller; Julia Vogt; Wolfgang Renz; Celal Ozerdem; Andreas Grässl; Valeriy Tkachenko; Jeanette Schulz-Menger; Thoralf Niendorf
2012-01-01
The sensitivity gain of ultrahigh field Magnetic Resonance (UHF-MR) holds the promise to enhance spatial and temporal resolution. Such improvements could be beneficial for cardiovascular MR. However, intracoronary stents used for treatment of coronary artery disease are currently considered to be contra-indications for UHF-MR. The antenna effect induced by a stent together with RF wavelength shortening could increase local radiofrequency (RF) power deposition at 7.0 T and bears the potential ...
Radio frequency probes for ultra-high field magnetic resonance imaging
Lee, Daniel James
2011-01-01
This thesis describes the design, construction and testing of a dome coil. The dome coil is hemispherical in shape and is intended to be used within a set of hemispherical gradient coils in a seven tesla magnetic resonance imaging magnet. The dome coil has eight independent elements and is designed to be used for parallel transmission and reception. It is shown that the dome coil produces less specific absorption rate than a conventional birdcage coil and is suitable for head imaging. A st...
Transient Schr\\"odinger-Poisson Simulations of a High-Frequency Resonant Tunneling Diode Oscillator
Mennemann, Jan-Frederik; Jüngel, Ansgar; Kosina, Hans
2012-01-01
Transient simulations of a resonant tunneling diode oscillator are presented. The semiconductor model for the diode consists of a set of time-dependent Schr\\"odinger equations coupled to the Poisson equation for the electric potential. The one-dimensional Schr\\"odinger equations are discretized by the finite-difference Crank-Nicolson scheme using memory-type transparent boundary conditions which model the injection of electrons from the reservoirs. This scheme is unconditionally stable and re...
International Nuclear Information System (INIS)
A novel flexible metamaterial narrow-band-pass filter is designed and proved to be reliable by both numerical simulations and experimental measurements. The unit cell of the designed structure consists of circle ring resonators on top of a thin dielectric layer backed by a metallic mesh. The investigations on the distribution of the surface current and magnetic field as well as the analysis of the equivalent circuit model reveal that the magnetic resonance response between layers induced by the reverse surface current contributes to the high quality factor band-pass property. Importantly, it is a flexible design with a tunable resonance frequency by just changing the radius of the circle rings and can also be easily extended to have the multi-band-pass property. Moreover, this simplified structure with low duty cycle and ultra-thin thickness is also a symmetric design which is insensitive to the polarization and incident angles. Therefore, such a metamaterial narrow-band-pass filter is of great importance in the practical applications such as filtering and radar stealth, and especially for the conformal structure applications in the infrared and optical window area. (paper)
Lin, Guoping
2015-01-01
Optical whispering gallery mode (WGM) resonators have been very attracting platforms for versatile Kerr frequency comb generations. We report a systematic study on the material dispersion of various optical materials that are capable of supporting quality factors above $10^9$. Using an analytical approximation of WGM resonant frequencies in disk resonators, we investigate the effect of the geometry and transverse mode order on the total group-velocity dispersion ($GVD$). We demonstrate that the major radii and the radial mode indices play an important role in tailoring the $GVD$ of WGM resonators. In particular, our study shows that in WGM disk-resonators, the polar families of modes have very similar $GVD$, while the radial families of modes feature dispersion values that can differ by up to several orders of magnitude. The effect of these giant dispersion shifts are experimentally evidenced in Kerr comb generation with magnesium fluoride. From a more general perspective, this critical feature enables to pus...
Zhou, Yan; Liu, Cheng-hui; Pu, Yang; Cheng, Gangge; Zhou, Lixin; Chen, Jun; Zhu, Ke; Alfano, Robert R.
2016-03-01
Raman spectroscopy has become widely used for diagnostic purpose of breast, lung and brain cancers. This report introduced a new approach based on spatial frequency spectra analysis of the underlying tissue structure at different stages of brain tumor. Combined spatial frequency spectroscopy (SFS), Resonance Raman (RR) spectroscopic method is used to discriminate human brain metastasis of lung cancer from normal tissues for the first time. A total number of thirty-one label-free micrographic images of normal and metastatic brain cancer tissues obtained from a confocal micro- Raman spectroscopic system synchronously with examined RR spectra of the corresponding samples were collected from the identical site of tissue. The difference of the randomness of tissue structures between the micrograph images of metastatic brain tumor tissues and normal tissues can be recognized by analyzing spatial frequency. By fitting the distribution of the spatial frequency spectra of human brain tissues as a Gaussian function, the standard deviation, σ, can be obtained, which was used to generate a criterion to differentiate human brain cancerous tissues from the normal ones using Support Vector Machine (SVM) classifier. This SFS-SVM analysis on micrograph images presents good results with sensitivity (85%), specificity (75%) in comparison with gold standard reports of pathology and immunology. The dual-modal advantages of SFS combined with RR spectroscopy method may open a new way in the neuropathology applications.
Trakic, Adnan; Weber, Ewald; Li, Bing Keong; Wang, Hua; Liu, Feng; Engstrom, Craig; Crozier, Stuart
2012-04-01
While recent studies have shown that rotating a single radio-frequency (RF) coil during the acquisition of magnetic resonance (MR) images provides a number of hardware advantages (i.e., requires only one RF channel, avoids coil-coil coupling and facilitates large-scale multinuclear imaging), they did not describe in detail how to build a rotating RF coil system. This paper presents detailed engineering information on the electromechanical design and construction of a MR-compatible RRFC system for human head imaging at 2 T. A custom-made (bladeless) pneumatic Tesla turbine was used to rotate the RF coil at a constant velocity, while an infrared optical encoder measured the selected frequency of rotation. Once the rotating structure was mechanically balanced and the compressed air supply suitably regulated, the maximum frequency of rotation measured ~14.5 Hz with a 2.4% frequency variation over time. MR images of a water phantom and human head were obtained using the rotating RF head coil system. PMID:22231668
Energy Technology Data Exchange (ETDEWEB)
Aerts, Hugo J W L [Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University, Maastricht (Netherlands); Jaspers, K; Backes, Walter H, E-mail: w.backes@mumc.nl [Department of Radiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University Medical Center (MUMC), Maastricht (Netherlands)
2011-09-07
Dynamic contrast-enhanced magnetic resonance imaging is increasingly applied for tumour diagnosis and early evaluation of therapeutic responses over time. However, the reliability of pharmacokinetic parameters derived from DCE-MRI is highly dependent on the experimental settings. In this study, the effect of sampling frequency (f{sub s}) and duration on the precision of pharmacokinetic parameters was evaluated based on system identification theory and computer simulations. Both theoretical analysis and simulations showed that a higher value of the pharmacokinetic parameter K{sup trans} required an increasing sampling frequency. For instance, for similar results, a relatively low f{sub s} of 0.2 Hz was sufficient for a low K{sup trans} of 0.1 min{sup -1}, compared to a high f{sub s} of 3 Hz for a high K{sup trans} of 0.5 min{sup -1}. For the parameter v{sub e}, a decreasing value required a higher sampling frequency. A sampling frequency below 0.1 Hz systematically resulted in imprecise estimates for all parameters. For the K{sup trans} and v{sub e} parameters, the sampling duration should be above 2 min, but durations of more than 7 min do not further improve parameter estimates.
Aerts, Hugo J. W. L.; Jaspers, K.; Backes, Walter H.
2011-09-01
Dynamic contrast-enhanced magnetic resonance imaging is increasingly applied for tumour diagnosis and early evaluation of therapeutic responses over time. However, the reliability of pharmacokinetic parameters derived from DCE-MRI is highly dependent on the experimental settings. In this study, the effect of sampling frequency (fs) and duration on the precision of pharmacokinetic parameters was evaluated based on system identification theory and computer simulations. Both theoretical analysis and simulations showed that a higher value of the pharmacokinetic parameter Ktrans required an increasing sampling frequency. For instance, for similar results, a relatively low fs of 0.2 Hz was sufficient for a low Ktrans of 0.1 min-1, compared to a high fs of 3 Hz for a high Ktrans of 0.5 min-1. For the parameter ve, a decreasing value required a higher sampling frequency. A sampling frequency below 0.1 Hz systematically resulted in imprecise estimates for all parameters. For the Ktrans and ve parameters, the sampling duration should be above 2 min, but durations of more than 7 min do not further improve parameter estimates.
Santamaría-Arrieta, Gorka; Brizuela-Velasco, Aritza; Fernández-González, Felipe J.; Chávarri-Prado, David; Chento-Valiente, Yelko; Solaberrieta, Eneko; Diéguez-Pereira, Markel; Yurrebaso-Asúa, Jaime
2016-01-01
Background This study evaluated the influence of implant site preparation depth on primary stability measured by insertion torque and resonance frequency analysis (RFA). Material and Methods Thirty-two implant sites were prepared in eight veal rib blocks. Sixteen sites were prepared using the conventional drilling sequence recommended by the manufacturer to a working depth of 10mm. The remaining 16 sites were prepared using an oversize drilling technique (overpreparation) to a working depth of 12mm. Bone density was determined using cone beam computerized tomography (CBCT). The implants were placed and primary stability was measured by two methods: insertion torque (Ncm), and RFA (implant stability quotient [ISQ]). Results The highest torque values were achieved by the conventional drilling technique (10mm). The ANOVA test confirmed that there was a significant correlation between torque and drilling depth (p0.05) at either measurement direction (cortical and medullar). No statistical relation between torque and ISQ values was identified, or between bone density and primary stability (p >0.05). Conclusions Vertical overpreparation of the implant bed will obtain lower insertion torque values, but does not produce statistically significant differences in ISQ values. Key words:Implant stability quotient, overdrilling, primary stability, resonance frequency analysis, torque.
Abbasi, Mohammad; Afkhami, Seyed E
2014-12-01
The resonant frequency and sensitivity of an atomic force microscope (AFM) with an assembled cantilever probe (ACP) is analyzed utilizing strain gradient theory, and then the governing equation and boundary conditions are derived by a combination of the basic equations of strain gradient theory and Hamilton's principle. The resonant frequency and sensitivity of the proposed AFM microcantilever are then obtained numerically. The proposed ACP includes a horizontal cantilever, two vertical extensions, and two tips located at the free ends of the extensions that form a caliper. As one of the extensions is located between the clamped and free ends of the AFM microcantilever, the cantilever is modeled as two beams. The results of the current model are compared with those evaluated by both modified couple stress and classical beam theories. The difference in results evaluated by the strain gradient theory and those predicted by the couple stress and classical beam theories is significant, especially when the microcantilever thickness is approximately the same as the material length-scale parameters. The results also indicate that at the low values of contact stiffness, scanning in the higher cantilever modes decrease the accuracy of the proposed AFM ACP. PMID:25205330
International Nuclear Information System (INIS)
The electron stretcher facility ELSA provides an electron beam of a few hundred pA used for the generation of bremsstrahlung photons probing the nucleon structure in a detector setup. For the correct interpretation of the events registered, the persistence of the beam position over time is crucial. Its continuous monitoring has been enabled by setting up a measurement system based on resonant cavities. Position signals at a frequency of 1.5 GHz and below one aW of power can be abstracted from the beam without degrading its quality. After frequency down-conversion to a few kHz, a narrow bandwidth detection performed by lock-in amplifiers separates them from noise. A maximum sample rate of 9 Hz and a resolution of one tenth of a millimeter could be achieved. The position signals have to be normalized to the beam current which is monitored by another dedicated resonator. The measurement precision down to a few pA allows for the accelerator extraction mechanism to be controlled by a feedback loop in order to obtain the respective requested current. (orig.)
Gao, Nansha; Wu, Jiu Hui; Yu, Lie; Xin, Hang
2016-10-01
Using FEM, we theoretically study the vibration properties of radial phononic crystal (RPC) with annular soft material. The band structures, transmission spectra, and displacement fields of eigenmode are given to estimate the starting and cut-off frequency of band gaps. Numerical calculation results show that RPC with annular soft material can yield low-frequency band gaps below 350 Hz. Annular soft material decreases equivalent stiffness of the whole structure effectively, and makes corresponding band gaps move to the lower frequency range. Physical mechanism behind band gaps is the coupling effect between long or traveling wave in plate matrix and the vibrations of corrugations. By changing geometrical dimensions of plate thickness e, the length of silicone rubber h2, and the corrugation width b, we can control the location and width of the first band gap. These research conclusions of RPC structure with annular soft material can potentially be applied to optimize band gaps, generate filters, and design acoustic devices.
Energy Technology Data Exchange (ETDEWEB)
Eriksson, Daniel
2010-07-01
Combustion of fuel in thermal power plants emits particles which creates coatings on the super heater tubes. The coatings isolate the tubes and impairs the efficiency of the heat transfer. Cleaning the tubes occurs while the power plant is running but without any knowledge of the actual coating. A change in frequency corresponds to a change in mass of the coatings. This thesis has been focusing in estimating resonance frequencies in vibration measurements made by strain gauges on the tubes. To improve the estimations a target tracking algorithm had been added. The results indicates that it is possible to estimate the resonance frequencies but the algorithms need to be verified on more signals.
Multipurpose High Frequency Electron Spin Resonance Spectrometer for Condensed Matter Research
Nagy, Kalman L; Quintavalle, Dario; Feher, Titusz; Janossy, Andras
2009-01-01
We describe a quasi-optical multifrequency ESR spectrometer operating in the 75-225 GHz range and optimized at 210 GHz for general use in condensed matter physics, chemistry and biology. The quasi-optical bridge detects the change of mm wave polarization at the ESR. A controllable reference arm maintains a mm wave bias at the detector. The attained sensitivity of 2x10^10 spin/G/(Hz)1/2, measured on a dilute Mn:MgO sample in a non-resonant probe head at 222.4 GHz and 300 K, is comparable to co...
Nonlinear beam clean-up using resonantly enhanced sum-frequency mixing
DEFF Research Database (Denmark)
Karamehmedovic, Emir; Pedersen, Christian; Jensen, Ole Bjarlin;
2009-01-01
We investigate the possibility of improving the beam quality and obtaining high conversion efficiency in nonlinear sum-frequency generation. A 765 nm beam from an external cavity tapered diode laser is single-passed through a nonlinear crystal situated in the high intracavity field of a 1342 nm N...
Transient Schrödinger-Poisson simulations of a high-frequency resonant tunneling diode oscillator
Mennemann, Jan-Frederik; Jüngel, Ansgar; Kosina, Hans
2013-04-01
Transient simulations of a resonant tunneling diode oscillator are presented. The semiconductor model for the diode consists of a set of time-dependent Schrödinger equations coupled to the Poisson equation for the electric potential. The one-dimensional Schrödinger equations are discretized by the finite-difference Crank-Nicolson scheme using memory-type transparent boundary conditions which model the injection of electrons from the reservoirs. This scheme is unconditionally stable and reflection-free at the boundary. An efficient recursive algorithm due to Arnold, Ehrhardt, and Sofronov is used to implement the transparent boundary conditions, enabling simulations which involve a very large number of time steps. Special care has been taken to provide a discretization of the boundary data which is completely compatible with the underlying finite-difference scheme. The transient regime between two stationary states and the self-oscillatory behavior of an oscillator circuit, containing a resonant tunneling diode, is simulated for the first time.
Duque, Daniel; Wang, Xin; Nieto-Diego, Javier; Krumbholz, Katrin; Malmierca, Manuel S
2016-04-12
Electrophysiological and psychophysical responses to a low-intensity probe sound tend to be suppressed by a preceding high-intensity adaptor sound. Nevertheless, rare low-intensity deviant sounds presented among frequent high-intensity standard sounds in an intensity oddball paradigm can elicit an electroencephalographic mismatch negativity (MMN) response. This has been taken to suggest that the MMN is a correlate of true change or "deviance" detection. A key question is where in the ascending auditory pathway true deviance sensitivity first emerges. Here, we addressed this question by measuring low-intensity deviant responses from single units in the inferior colliculus (IC) of anesthetized rats. If the IC exhibits true deviance sensitivity to intensity, IC neurons should show enhanced responses to low-intensity deviant sounds presented among high-intensity standards. Contrary to this prediction, deviant responses were only enhanced when the standards and deviants differed in frequency. The results could be explained with a model assuming that IC neurons integrate over multiple frequency-tuned channels and that adaptation occurs within each channel independently. We used an adaptation paradigm with multiple repeated adaptors to measure the tuning widths of these adaption channels in relation to the neurons' overall tuning widths.
Robust adaptive controller design for a class of nonlinear systems with unknown high frequency gains
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
In this note, a robust adaptive control scheme is proposed for a class of nonlinear systems that have unknown multiplicative terms. Unlike previous results, except for the unknown control directions, we do not require a priori bounds on the unknown parameters. We also allow the unknown parameters to be time-varying provided that they are bounded. Our proposed robust adaptive controller is designed to identify on-line the unknown control directions and is a switching type controller, in which the controller parameters are tuned in a switching manner via a switching logic. Global stability of the closed-loop systems have been proved.
Adaptive Noise Cancellation System for Low Frequency Transmission of Sound in Open Fan Aircraft
Directory of Open Access Journals (Sweden)
Steven Griffin
2013-01-01
Full Text Available This paper describes the use of a structural/acoustic model of a section of a large aircraft to help define the sensor/actuator architecture that was used in a hardware demonstration of adaptive noise cancellation. Disturbances considered were representative of propeller-induced disturbances from an open fan aircraft. Controller on and controller off results from a hardware demonstration on a portion of a large aircraft are also included. The use of the model has facilitated the development of a new testing technique, closely related to modal testing, that can be used to find good structural actuator locations for adaptive noise cancellation.
Damping of Inter-Area Low Frequency Oscillation Using an Adaptive Wide-Area Damping Controller
DEFF Research Database (Denmark)
Yao, Wei; Jiang, L.; Fang, Jiakun;
2013-01-01
in each sampling interval. Case studies are undertaken on a two-area fourmachine power system and the New England 10-machine 39-bus power system, respectively. Simulation results show that the proposed adaptive WADC not only can damp the inter-area oscillations effectively under a wide range of operation...
Frequency of bone-bruises in ankle sprains. Magnetic resonance imaging studies
Energy Technology Data Exchange (ETDEWEB)
Uto, Yuji; Morooka, Masaaki [Morooka Orthopaedic Surgery Hospital, Fukuoka (Japan)
2002-09-01
We retrospectively studied MRI on the frequency of bone-bruises in ankle sprains, especially those of the lateral collateral ligaments of the ankle joint. Bone-bruises occurred in 3.8% (4/106) of ruptures of anterior talofibular ligament (ATFL), and 6.3% (5/79) of ruptures of ATFL and calcaneofibular ligament (CFL). Bone-bruises were more likely to be seen in ATFL and CFL ruptures than in ATFL rupture alone. (author)
Frequency of bone-bruises in ankle sprains. Magnetic resonance imaging studies
International Nuclear Information System (INIS)
We retrospectively studied MRI on the frequency of bone-bruises in ankle sprains, especially those of the lateral collateral ligaments of the ankle joint. Bone-bruises occurred in 3.8% (4/106) of ruptures of anterior talofibular ligament (ATFL), and 6.3% (5/79) of ruptures of ATFL and calcaneofibular ligament (CFL). Bone-bruises were more likely to be seen in ATFL and CFL ruptures than in ATFL rupture alone. (author)
Directory of Open Access Journals (Sweden)
Marie Ramon
2009-01-01
Full Text Available Systematic lossy error protection (SLEP is a robust error resilient mechanism based on principles of Wyner-Ziv (WZ coding for video transmission over error-prone networks. In an SLEP scheme, the video bitstream is separated into two parts: a systematic part consisting of a video sequence transmitted without channel coding, and additional information consisting of a WZ supplementary stream. This paper presents an adaptive SLEP scheme in which the WZ stream is obtained by frequency filtering in the transform domain. Additionally, error resilience varies adaptively depending on the characteristics of compressed video. We show that the proposed SLEP architecture achieves graceful degradation of reconstructed video quality in the presence of increasing transmission errors. Moreover, it provides good performances in terms of error protection as well as reconstructed video quality if compared to solutions based on coarser quantization, while offering an interesting embedded scheme to apply digital video format conversion.
Bargatze, L. F.
2015-12-01
Active Data Archive Product Tracking (ADAPT) is a collection of software routines that permits one to generate XML metadata files to describe and register data products in support of the NASA Heliophysics Virtual Observatory VxO effort. ADAPT is also a philosophy. The ADAPT concept is to use any and all available metadata associated with scientific data to produce XML metadata descriptions in a consistent, uniform, and organized fashion to provide blanket access to the full complement of data stored on a targeted data server. In this poster, we present an application of ADAPT to describe all of the data products that are stored by using the Common Data File (CDF) format served out by the CDAWEB and SPDF data servers hosted at the NASA Goddard Space Flight Center. These data servers are the primary repositories for NASA Heliophysics data. For this purpose, the ADAPT routines have been used to generate data resource descriptions by using an XML schema named Space Physics Archive, Search, and Extract (SPASE). SPASE is the designated standard for documenting Heliophysics data products, as adopted by the Heliophysics Data and Model Consortium. The set of SPASE XML resource descriptions produced by ADAPT includes high-level descriptions of numerical data products, display data products, or catalogs and also includes low-level "Granule" descriptions. A SPASE Granule is effectively a universal access metadata resource; a Granule associates an individual data file (e.g. a CDF file) with a "parent" high-level data resource description, assigns a resource identifier to the file, and lists the corresponding assess URL(s). The CDAWEB and SPDF file systems were queried to provide the input required by the ADAPT software to create an initial set of SPASE metadata resource descriptions. Then, the CDAWEB and SPDF data repositories were queried subsequently on a nightly basis and the CDF file lists were checked for any changes such as the occurrence of new, modified, or deleted
International Nuclear Information System (INIS)
Purpose. To assess the role of image parameters derived from dynamic contrast enhanced magnetic resonance imaging (DCEMRI) in bladder cancer staging, and to investigate the potential use of such parameter images in biological image-adapted radiotherapy (RT). Materials and methods. High-resolution volumetric interpolated breath-hold (VIBE) DCEMRI of 26 patients diagnosed with bladder cancer was performed. DCEMRI parameters derived from tumor and muscle contrast uptake curves were extracted and subjected to correlation analysis with tumor volume as well as clinical, pathological, histological and T2-weighted MR tumor stage. For parameters showing a significant correlation with tumor stage, 3D malignancy maps were generated. As an initial step towards delivery of biologically adapted intensity modulated radiotherapy (IMRT) it was hypothesized that the malignancy map could be used as a RT dose prescription map. Simulating IMRT delivery with multi-leaf collimators (MLCs), idealized dose distributions, constituted by dose cubes, were adapted to the prescription map. The size of the dose cubes were varied to mimic MLCs of varying leaf width. The difference between the adapted and prescribed dose distributions was quantified by the root mean square deviation (RMSD). Results. No significant relationships were found between tumor volume and extracted DCEMRI parameters. The normalized area between tumor and muscle contrast uptake curves (nABC) evaluated from 0-180 seconds (nABC180) and 0-480s (nABC480) correlated significantly with tumor stage (p=0.047 and p=0.035, respectively). Dose prescription maps for 10 patients were generated from the nABC480. The RMSD between the prescribed and adapted dose distribution decreased with decreasing size of the dose cubes. Large interpatient variations in the RMSD and in the dependence of the RMSD on different dose cube sizes were found. Conclusions. The nABC180 and nABC480 may provide added value in staging of bladder cancer. High
Ferromagnetic resonance of a YIG film in the low frequency regime
Ketterson, John; Grudichak, Scott; Sklenar, Joseph; Tsai, C. C.; Jang, Moongyu; Yang, Qinghui; Zhang, Huaiwu; Lee, Seongjae
An improved method for characterizing the magnetic anisotropy of films with cubic symmetry is described and is applied to an yttrium iron garnet (111) film. Analysis of the FMR spectra performed both in-plane and out-of-plane from 0.7 to 8 GHz yielded the magnetic anisotropy constants as well as the saturation magnetization. The field at which FMR occurs is sensitive to anisotropy constants in the low frequency (Sciences, Materials Science and Engineering Division under Grant Number DE-SC0014424. The film growth was supported by the National Natural Science Foundation of China (NSFC) under Grants 51272036 and 51002021 and 51472046.
Tanaka, Yoshihito; Lin, S.; Aono, M.; Suzuki, T.
The spectral profiles of sum-frequency signal from CH vibrational modes of octadecanethiol (ODT) self-assembled on gold have been studied for several optical configurations of incident beams. The observed spectra, generally of the shape of dispersion type, have been interpreted by the interference between the resonant contribution from the CH stretching modes of adsorbed molecules and the nonresonant contribution from the gold substrate. We have shown for the first time that the contribution from the zzz component of the resonant nonlinear susceptibility χzzz(R) is dominant in the observed resonant signals, whereas all of the ijk components contribute to the nonresonant signal. The transition frequencies and the relative amplitude of resonant signals are also determined for the CH3 vibrational modes of ODT on gold.
Kurth, W. S.; Frank, L. A.; Gurnett, D. A.; Burek, B. G.; Ashour-Abdalla, M.
1980-01-01
Significant progress has been made in understanding intense electrostatic waves near the upper hybrid resonance frequency in terms of the theory of multiharmonic cyclotron emission using a classical loss-cone distribution function as a model. Recent observations by Hawkeye 1 and GEOS 1 have verified the existence of loss-cone distributions in association with the intense electrostatic wave events, however, other observations by Hawkeye and ISEE have indicated that loss cones are not always observable during the wave events, and in fact other forms of free energy may also be responsible for the instability. Now, for the first time, a positively sloped feature in the perpendicular distribution function has been uniquely identified with intense electrostatic wave activity. Correspondingly, we suggest that the theory is flexible under substantial modifications of the model distribution function.
Auzinsh, Marcis; Ferber, Ruvin; Gahbauer, Florian; Kalvans, Linards; Mozers, Arturs; Spiss, Agris
2013-01-01
We studied magneto-optical resonances caused by excited-state level crossings in a nonzero magnetic field. Experimental measurements were performed on the transitions of the $D_2$ line of rubidium. These measured signals were described by a theoretical model that takes into account all neighboring hyperfine transitions, the mixing of magnetic sublevels in an external magnetic field, the coherence properties of the exciting laser radiation, and the Doppler effect. Good agreement between the experimental measurements and the theoretical model could be achieved over a wide range of laser power densities. We further showed that the contrasts of the level-crossing peaks can be sensitive to changes in the frequency of the exciting laser radiation as small as several tens of megahertz when the hyperfine splitting of the exciting state is larger than the Doppler broadening.
Ballester, Ernest Alsina; Bueno, Javier Trujillo
2016-01-01
The spectral line polarization encodes a wealth of information about the thermal and magnetic properties of the solar atmosphere. Modeling the Stokes profiles of strong resonance lines is, however, a complex problem both from the theoretical and computational point of view, especially when partial frequency redistribution (PRD) effects need to be taken into account. In this work, we consider a two-level atom in the presence of magnetic fields of arbitrary intensity (Hanle-Zeeman regime) and orientation, both deterministic and micro-structured. Working within the framework of a rigorous PRD theoretical approach, we have developed a numerical code which solves the full non-LTE radiative transfer problem for polarized radiation, in one-dimensional models of the solar atmosphere, accounting for the combined action of the Hanle and Zeeman effects, as well as for PRD phenomena. After briefly discussing the relevant equations, we describe the iterative method of solution of the problem and the numerical tools that w...
Stuchlik, Zdenek; Torok, Gabriel
2013-01-01
Using known frequencies of the twin-peak high-frequency quasiperiodic oscillations (HF QPOs) and known mass of the central black hole, the black-hole dimensionless spin can be determined by assuming a concrete version of the resonance model. However, a wide range of observationally limited values of the black hole mass implies low precision of the spin estimates. We discuss the possibility of higher precision of the black hole spin measurements in the framework of a multi-resonance model inspired by observations of more than two HF QPOs in the black hole systems, which are expected to occur at two (or more) different radii of the accretion disc. For the black hole systems we focus on the special case of duplex frequencies, when the top, bottom, or mixed frequency is common at two different radii where the resonances occur giving triple frequency sets. The sets of triple frequency ratios and the related spin are given. The strong resonance model for "magic" values of the black hole spin means that two (or more...
Directory of Open Access Journals (Sweden)
Marcello Mancini
Full Text Available To characterize the anatomy of the venous outflow of the mouse brain using different imaging techniques. Ten C57/black male mice (age range: 7-8 weeks were imaged with high-frequency Ultrasound, Magnetic Resonance Angiography and ex-vivo Microcomputed tomography of the head and neck. Under general anesthesia, Ultrasound of neck veins was performed with a 20 MHz transducer; head and neck Magnetic Resonance Angiography data were collected on 9.4 T or 7 T scanners, and ex-vivo Microcomputed tomography angiography was obtained by filling the vessels with a radiopaque inert silicone rubber compound. All procedures were approved by the local ethical committee. The dorsal intracranial venous system is quite similar in mice and humans. Instead, the mouse Internal Jugular Veins are tiny vessels receiving the sigmoid sinuses and tributaries from cerebellum, occipital lobe and midbrain, while the majority of the cerebral blood, i.e. from the olfactory bulbs and fronto-parietal lobes, is apparently drained through skull base connections into the External Jugular Vein. Three main intra-extracranial anastomoses, absent in humans, are: 1 the petrosquamous sinus, draining into the posterior facial vein, 2 the veins of the olfactory bulb, draining into the superficial temporal vein through a foramen of the frontal bone 3 the cavernous sinus, draining in the External Jugular Vein through a foramen of the sphenoid bone. The anatomical structure of the mouse cranial venous outflow as depicted by Ultrasound, Microcomputed tomography and Magnetic Resonance Angiography is different from humans, with multiple connections between intra- and extra-cranial veins.
Mancini, Marcello; Greco, Adelaide; Tedeschi, Enrico; Palma, Giuseppe; Ragucci, Monica; Bruzzone, Maria Grazia; Coda, Anna Rita Daniela; Torino, Enza; Scotti, Alessandro; Zucca, Ileana; Salvatore, Marco
2015-01-01
To characterize the anatomy of the venous outflow of the mouse brain using different imaging techniques. Ten C57/black male mice (age range: 7-8 weeks) were imaged with high-frequency Ultrasound, Magnetic Resonance Angiography and ex-vivo Microcomputed tomography of the head and neck. Under general anesthesia, Ultrasound of neck veins was performed with a 20 MHz transducer; head and neck Magnetic Resonance Angiography data were collected on 9.4 T or 7 T scanners, and ex-vivo Microcomputed tomography angiography was obtained by filling the vessels with a radiopaque inert silicone rubber compound. All procedures were approved by the local ethical committee. The dorsal intracranial venous system is quite similar in mice and humans. Instead, the mouse Internal Jugular Veins are tiny vessels receiving the sigmoid sinuses and tributaries from cerebellum, occipital lobe and midbrain, while the majority of the cerebral blood, i.e. from the olfactory bulbs and fronto-parietal lobes, is apparently drained through skull base connections into the External Jugular Vein. Three main intra-extracranial anastomoses, absent in humans, are: 1) the petrosquamous sinus, draining into the posterior facial vein, 2) the veins of the olfactory bulb, draining into the superficial temporal vein through a foramen of the frontal bone 3) the cavernous sinus, draining in the External Jugular Vein through a foramen of the sphenoid bone. The anatomical structure of the mouse cranial venous outflow as depicted by Ultrasound, Microcomputed tomography and Magnetic Resonance Angiography is different from humans, with multiple connections between intra- and extra-cranial veins. PMID:26067061
Torrezan, Antonio C; Han, Seong-Tae; Mastovsky, Ivan; Shapiro, Michael A; Sirigiri, Jagadishwar R; Temkin, Richard J; Barnes, Alexander B; Griffin, Robert G
2010-06-01
The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE(11,2) and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE(11,2,q). The minimum start current is 27 mA. Power and frequency tuning measurements as a function of the electron cyclotron frequency have also been carried out. A smooth frequency tuning range of 1 GHz was obtained for the operating second-harmonic mode either by magnetic field tuning or beam voltage tuning. Long-term CW operation was evaluated during an uninterrupted period of 48 h, where the gyrotron output power and frequency were kept stable to within ±0.7% and ±6 ppm, respectively, by a computerized control system. Proper operation of an internal quasi-optical mode converter implemented to transform the operating whispering-gallery mode to a Gaussian-like beam was also verified. Based on the images of the gyrotron output beam taken with a pyroelectric camera, the Gaussian-like mode content of the output beam was computed to be 92% with an ellipticity of 12%. PMID:21243088
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Tobias Riede
Full Text Available BACKGROUND: In many songbirds the larger vocal repertoire of males is associated with sexual dimorphism of the vocal control centers and muscles of the vocal organ, the syrinx. However, it is largely unknown how these differences are translated into different acoustic behavior. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that the sound generating structures of the syrinx, the labia and the associated cartilaginous framework, also display sexual dimorphism. One of the bronchial half rings that position and tense the labia is larger in males, and the size and shape of the labia differ between males and females. The functional consequences of these differences were explored by denervating syringeal muscles. After denervation, both sexes produced equally low fundamental frequencies, but the driving pressure generally increased and was higher in males. Denervation strongly affected the relationship between driving pressure and fundamental frequency. CONCLUSIONS/SIGNIFICANCE: The syringeal modifications in the male syrinx, in concert with dimorphisms in neural control and muscle mass, are most likely the foundation for the potential to generate an enhanced frequency range. Sexually dimorphic vocal behavior therefore arises from finely tuned modifications at every level of the motor cascade. This sexual dimorphism in frequency control illustrates a significant evolutionary step towards increased vocal complexity in birds.
Abedian, Behrouz; Cundari, Michael
1993-07-01
This work presents experimental and theoretical results on the dynamic behavior of piezoelectric cantilever bimorph in the presence of surrounding air. The bimorph is composed of a pair of piezoelectric sheets bonded by a uniform elastic layer of adhesive in the center. The transverse motion of the bimorph is generated by a sequential application of two opposing electric fields on the piezoelectric sheets. Theoretically, the tip deflection and the natural frequency of the bimorph are obtained making use of an energy balance technique. The fluid in modeled as inviscid and incompressible whose motion induces locally additional mass in the transverse direction. An expression for the kinetic energy of the system is derived based on this additional mass from which the natural frequency of the combined system is obtained. Tests were performed on the piezoelectric bimorphs with similar geometries and varying adhesive thickness in a vacuum chamber. The air pressure in the chamber was varied from 10 kPa to one atmosphere. Good agreements between the theoretical predictions and the observed values were obtained. This study could have applications in the use of piezoelectric materials for fluid property measurements.
Tuan, Tran Thanh; Vinh, Pham Chi; Ohrnberger, Matthias; Malischewsky, Peter; Aoudia, Abdelkrim
2016-05-01
The resonance frequency of the transmission response in layered half-space model is important in the study of site effect because it is the frequency where the shake-ability of the ground is enhanced significantly. In practice, it is often determined by the H/V ratio technique in which the peak frequency of recorded H/V spectral ratio is interpreted as the resonance frequency. Despite of its importance, there has not been any formula of the resonance frequency of the layered half-space structure. In this paper, a simple approximate formula of the fundamental resonance frequency is presented after an exact formula in explicit form of the response function of vertically SH incident wave is obtained. The formula is in similar form with the one used in H/V ratio technique but it reflects several major effects of the model to the resonance frequency such as the arrangement of layers, the impedance contrast between layers and the half-space. Therefore, it could be considered as an improved formula used in H/V ratio technique. The formula also reflects the consistency between two approaches of the H/V ratio technique based on SH body waves or Rayleigh surface waves on the peak frequency under high impedance contrast condition. This formula is in explicit form and, therefore, may be used in the direct and inverse problem efficiently. A numerical illustration of the improved formula for an actual layered half-space model already investigated by H/V ratio technique is presented to demonstrate its new features and its improvement to the currently used formula.