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.
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 frequency in ferromagnetic superlattices
Energy Technology Data Exchange (ETDEWEB)
Qiu Rongke; Huang Andong [School of Science, Shenyang University of Technology, Shenyang 110870 (China); Li Da; Zhang Zhidong, E-mail: rkqiu@163.com [Shenyang National Laboratory for Materials Science, Institute of Metal Research and International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016 (China)
2011-10-19
The resonance frequency in two-layer and three-layer ferromagnetic superlattices is studied, using the Callen's Green function method, the Tyablikov decoupling approximation and the Anderson-Callen decoupling approximation. The effects of interlayer exchange coupling, anisotropy, external magnetic field and temperature on the resonance frequency are investigated. It is found that the resonance frequencies increase with increasing external magnetic field. In a parameter region of the asymmetric system, each sublayer corresponds to its own resonance frequency. The anisotropy of a sublayer affects only the resonance frequency corresponding to this sublayer. The stronger the anisotropy, the higher is the resonance frequency. The interlayer exchange coupling affects only the resonance frequencies belonging to the sublayers connected by it. The stronger the interlayer exchange coupling, the higher are the resonance frequencies. All the resonance frequencies decrease as the reduced temperature increases. The results direct the method to enhance and adjust the resonance frequency of magnetic multilayered materials with a wide band.
Frequency Resonance in Stochastic Systems
Institute of Scientific and Technical Information of China (English)
钱敏; 张雪娟
2003-01-01
The phenomenon of frequency resonance, which is usually related to deterministic systems, is investigated in stochastic systems. We show that for those autonomous systems driven only by white noise, if the output power spectrum exhibits a nonzero peak frequency, then applying a periodic signel just on this noise-induced central frequency can also induce a resonance phenomenon, which we call the frequency stochastic resonance. The effect of such a resonance in a coupled stochastic system is shown to be much better than that in a single-oscillator system.
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.
Fast Resonance Frequency Modulation in Superconducting Stripline Resonator
Segev, Eran; Abdo, Baleegh; Shtempluck, Oleg; Buks, Eyal
2006-01-01
Fast resonance frequency modulation of a superconducting stripline resonator is investigated. The experiments are performed using a novel device which integrates a hot electron detector (HED) into a superconducting stripline ring resonator. Frequency modulation is demonstrated by both applying dc current or voltage to the HED, and by applying optical illumination, with modulation frequencies of up to 4.2GHz. Potential applications for such a device are in telecommunication, quantum cryptograp...
Novel resonant cantilever mass change detection and resonant frequency tuning
DEFF Research Database (Denmark)
Grigorov, Alexander; Boisen, Anja
2005-01-01
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 stru...
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...
Frequency domain FIR and IIR adaptive filters
Lynn, D. W.
1990-01-01
A discussion of the LMS adaptive filter relating to its convergence characteristics and the problems associated with disparate eigenvalues is presented. This is used to introduce the concept of proportional convergence. An approach is used to analyze the convergence characteristics of block frequency-domain adaptive filters. This leads to a development showing how the frequency-domain FIR adaptive filter is easily modified to provide proportional convergence. These ideas are extended to a block frequency-domain IIR adaptive filter and the idea of proportional convergence is applied. Experimental results illustrating proportional convergence in both FIR and IIR frequency-domain block adaptive filters is presented.
On Frequency Combs in Monolithic Resonators
Savchenkov, A. A.; Matsko, A. B.; Maleki, L.
2016-06-01
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.
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.
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.
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
Adaptive Backstepping Control of Resonant Frequency Based on DRFNN%基于动态递归模糊神经网络的共振频率自适应反推控制
Institute of Scientific and Technical Information of China (English)
张平均; 蒋新华
2011-01-01
For the non-linear and parameter uncertainties of the resonant frequency controlling system of resonant machine, the adaptive back-stepping control method combined with the dynamic recurrent fuzzy neural network (DRFNN) is studied.A mathematic model of the resonant frequency controlling system is presented firstly, and the control law is designed based on adaptive back-stepping method with regardless of the parameter uncertainties.Next, the parameter uncertainties of the electro-hydraulic proportional system which affect the frequency controlling performance are defined as items to be estimated using DRFNN, the parameter adjustment law is given based on DRFNN method, and the convergence of output tracking is proved through Lyapunov function.Finally, the results from simulated experiment and test on vehicle show that this method has a better resonant frequency controlling performance for the parameter uncertainties and the load disturbance.%针对共振破碎机频率控制系统的非线性和参数不确定性问题,提出基于动态递归模糊神经网络的自适应反推控制策略.建立了破碎机频率控制系统的数学模型,在忽略不确定性项的前提下,设计了基于自适应反推方法控制律.其次将电液比例系统中影响频率控制性能的不确定性因素定义为待估计项,采用动态递归模糊神经网络对其进行估计,给出了基于动态递归模糊神经网络的参数自适应律,并通过Lyapunov方法证明了输出跟踪的收敛性.仿真实验和车载测试结果表明,对于参数的不确定性和负载扰动,该方法具有较好的频率控制性能.
Auditory adaptation improves tactile frequency perception.
Crommett, Lexi E; Pérez-Bellido, Alexis; Yau, Jeffrey M
2017-01-11
Our ability to process temporal frequency information by touch underlies our capacity to perceive and discriminate surface textures. Auditory signals, which also provide extensive temporal frequency information, can systematically alter the perception of vibrations on the hand. How auditory signals shape tactile processing is unclear: perceptual interactions between contemporaneous sounds and vibrations are consistent with multiple neural mechanisms. Here we used a crossmodal adaptation paradigm, which separated auditory and tactile stimulation in time, to test the hypothesis that tactile frequency perception depends on neural circuits that also process auditory frequency. We reasoned that auditory adaptation effects would transfer to touch only if signals from both senses converge on common representations. We found that auditory adaptation can improve tactile frequency discrimination thresholds. This occurred only when adaptor and test frequencies overlapped. In contrast, auditory adaptation did not influence tactile intensity judgments. Thus, auditory adaptation enhances touch in a frequency- and feature-specific manner. A simple network model in which tactile frequency information is decoded from sensory neurons that are susceptible to auditory adaptation recapitulates these behavioral results. Our results imply that the neural circuits supporting tactile frequency perception also process auditory signals. This finding is consistent with the notion of supramodal operators performing canonical operations, like temporal frequency processing, regardless of input modality.
High-frequency micromechanical columnar resonators
Directory of Open Access Journals (Sweden)
Jenny Kehrbusch, Elena A Ilin, Peter Bozek, Bernhard Radzio and Egbert Oesterschulze
2009-01-01
Full Text Available High-frequency silicon columnar microresonators are fabricated using a simple but effective technological scheme. An optimized fabrication scheme was invented to obtain mechanically protected microcolumns with lateral dimensions controlled on a scale of at least 1 μm. In this paper, we investigate the influence of the environmental conditions on the mechanical resonator properties. At ambient conditions, we observed a frequency stability δf/f of less than 10−6 during 5 h of operation at almost constant temperature. However, varying the temperature shifts the frequency by approximately −173 Hz °C− 1. In accordance with a viscous damping model of the ambient gas, we perceived that the quality factor of the first flexural mode decreased with the inverse of the square root of pressure. However, in the low-pressure regime, a linear dependence was observed. We also investigated the influence of the type of the immersing gas on the resonant frequency.
Frequency division using a micromechanical resonance cascade
Energy Technology Data Exchange (ETDEWEB)
Qalandar, K. R., E-mail: kamala@engineering.ucsb.edu; Gibson, B.; Sharma, M.; Ma, A.; Turner, K. L. [Department of Mechanical Engineering, University of California at Santa Barbara, Santa Barbara, California 93106 (United States); Strachan, B. S. [Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan 48823 (United States); Department of Electrical Engineering, Michigan State University, East Lansing, Michigan 48823 (United States); Shaw, S. W. [Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan 48823 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48823 (United States)
2014-12-15
A coupled micromechanical resonator array demonstrates a mechanical realization of multi-stage frequency division. The mechanical structure consists of a set of N sequentially perpendicular microbeams that are connected by relatively weak elastic elements such that the system vibration modes are localized to individual microbeams and have natural frequencies with ratios close to 1:2:⋯:2{sup N}. Conservative (passive) nonlinear inter-modal coupling provides the required energy transfer between modes and is achieved by finite deformation kinematics. When the highest frequency beam is excited, this arrangement promotes a cascade of subharmonic resonances that achieve frequency division of 2{sup j} at microbeam j for j = 1, …, N. Results are shown for a capacitively driven three-stage divider in which an input signal of 824 kHz is passively divided through three modal stages, producing signals at 412 kHz, 206 kHz, and 103 kHz. The system modes are characterized and used to delineate the range of AC input voltages and frequencies over which the cascade occurs. This narrow band frequency divider has simple design rules that are scalable to higher frequencies and can be extended to a larger number of modal stages.
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.
Electrothermal Frequency Modulated Resonator for Mechanical Memory
Hafiz, Md Abdullah Al
2016-08-18
In this paper, we experimentally demonstrate a mechanical memory device based on the nonlinear dynamics of an electrostatically actuated microelectromechanical resonator utilizing an electrothermal frequency modulation scheme. The microstructure is deliberately fabricated as an in-plane shallow arch to achieve geometric quadratic nonlinearity. We exploit this inherent nonlinearity of the arch and drive it at resonance with minimal actuation voltage into the nonlinear regime, thereby creating softening behavior, hysteresis, and coexistence of states. The hysteretic frequency band is controlled by the electrothermal actuation voltage. Binary values are assigned to the two allowed dynamical states on the hysteretic response curve of the arch resonator with respect to the electrothermal actuation voltage. Set-and-reset operations of the memory states are performed by applying controlled dc pulses provided through the electrothermal actuation scheme, while the read-out operation is performed simultaneously by measuring the motional current through a capacitive detection technique. This novel memory device has the advantages of operating at low voltages and under room temperature. [2016-0043
Effect of metal coating and residual stress on the resonant frequency of MEMS resonators
Pandey, Ashok Kumar; Venkatesh, KP; Pratap, Rudra
2009-01-01
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 t...
Magnetodielectric effect of Mn–Zn ferrite at resonant frequency
Energy Technology Data Exchange (ETDEWEB)
Pengfei, Pan; Ning, Zhang, E-mail: zhangning@njnu.edu.cn
2016-10-15
The dielectric properties and the magnetodielectric effect in Mn–Zn ferrite at resonant frequency have been studied in this paper. Dimensional-resonance-induced abnormal dielectric spectrum was observed at f≈1 MHz. The relatively large magnetodielectric ratio of 4500% in a magnetic field of 3.5 kOe was achieved from the Mn–Zn ferrite sample with the initial permeability of 15 K at resonant frequency at room temperature. Theoretical analysis suggests that the large MD effect at resonant frequency is attributed to the enhanced magnetostriction effect. - Highlights: • Dimensional resonance was measured in dielectric spectrum at f≈1 MHz. • The MD ratio of 4500% was induced by H = 3.5 kOe at resonant frequency. • The magnetostriction effect leads to the large MD effect at resonant frequency.
Multi-Frequency Resonances in Pure Multiple-Pulse NQR
Energy Technology Data Exchange (ETDEWEB)
Furman, G. B., E-mail: gregoryf@bgu.ac.il [Ben-Gurion University (Israel); Kibrik, G. E.; Polyakov, A. Yu. [Perm State University (Russian Federation)
2004-12-15
We have observed multi-frequency resonances in a system with a spin 3/2 irradiated simultaneously by a multiple-pulse radiofrequency sequence and a low frequency field swept in the range 0 - 80 kHz. The theoretical description of the effect is presented using both the rotating frame approximation and the Floquet theory. Both approaches give indentical results at the calculation of the resonance frequencies, transition probabilities and shifts of resonance frequency. The calculated magnetization vs. the frequency of the low-frequency field agrees with the obtained experimental data.
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.
Magnetodielectric effect of Mn-Zn ferrite at resonant frequency
Pengfei, Pan; Ning, Zhang
2016-10-01
The dielectric properties and the magnetodielectric effect in Mn-Zn ferrite at resonant frequency have been studied in this paper. Dimensional-resonance-induced abnormal dielectric spectrum was observed at f≈1 MHz. The relatively large magnetodielectric ratio of 4500% in a magnetic field of 3.5 kOe was achieved from the Mn-Zn ferrite sample with the initial permeability of 15 K at resonant frequency at room temperature. Theoretical analysis suggests that the large MD effect at resonant frequency is attributed to the enhanced magnetostriction effect.
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
Development of adaptive resonator techniques for high-power lasers
Energy Technology Data Exchange (ETDEWEB)
An, J; Brase, J; Carrano, C; Dane, C B; Flath, L; Fochs, S; Hurd, R; Kartz, M; Sawvel, R
1999-07-12
The design of an adaptive wavefront control system for a high-power Nd:Glass laser will be presented. Features of this system include: an unstable resonator in confocal configuration, a multi-module slab amplifier, and real-time intracavity adaptive phase control using deformable mirrors and high-speed wavefront sensors. Experimental results demonstrate the adaptive correction of an aberrated passive resonator (no gain).
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.
Hao, T; Edwards, D J; Stevens, C J
2008-01-01
Methods on reducing resonant frequencies and electrical sizes of resonators are reported in this paper. Theoreti-cal and numerical analysis has been used and the results for the broadside-coupled resonators from both studies exhibit good agreement. Initial fabrication techniques are proposed and measurement results are compared with simulations. Further high resolution techniques have been envisaged to enhance the performance of the resona-tors. This class of small resonators with low resonant frequencies indicates a variety of applications in the design of microwave devices.
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...
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.
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.
Frequency modulated weak signal detection based on stochastic resonance and genetic algorithm
Institute of Scientific and Technical Information of China (English)
XING; Hongyan; LU; Chunxia; ZHANG; Qiang
2016-01-01
Stochastic resonance system is subject to the restriction of small frequency parameter in weak signal detection,in order to solve this problem,a frequency modulated weak signal detection method based on stochastic resonance and genetic algorithm is presented in this paper. The frequency limit of stochastic resonance is eliminated by introducing carrier signal,which is multiplied with the measured signal to be injected in the stochastic resonance system,meanwhile,using genetic algorithm to optimize the carrier signal frequency,which determine the generated difference-frequency signal in the lowfrequency range,so as to achieve the stochastic resonance weak signal detection. Results showthat the proposed method is feasible and effective,which can significantly improve the output SNR of stochastic resonance,in addition,the system has the better self-adaptability,according to the operation result and output phenomenon,the unknown frequency of the signal to be measured can be obtained,so as to realize the weak signal detection of arbitrary frequency.
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.
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.
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.
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.
Method and apparatus for resonant frequency waveform modulation
Taubman, Matthew S [Richland, WA
2011-06-07
A resonant modulator device and process are described that provide enhanced resonant frequency waveforms to electrical devices including, e.g., laser devices. Faster, larger, and more complex modulation waveforms are obtained than can be obtained by use of conventional current controllers alone.
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
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.
Resonances in BSO with frequency shifted input beams
DEFF Research Database (Denmark)
Buchhave, Preben; Vasnetsov, M.; Lyuksyutov, S.
1996-01-01
In this publication we report experiments with a frequency modulated offset frequency, which illustrate in which situations the problem may be considered linear, and in which it may not. Surprisingly we find, that even in the region of subharmonic generation, the space-charge field of the primary...... frequencies. We also report how resonances, forced by even a weak modulation of the frequency detuning may cause the suppression of the subharmonic generation....
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.
Hysteresis of the resonance frequency of magnetostrictive bending cantilevers
Löffler, Michael; Kremer, Ramona; Sutor, Alexander; Lerch, Reinhard
2015-05-01
Magnetostrictive bending cantilevers are applicable for wirelessly measuring physical quantities such as pressure and strain. Exploiting the ΔE-effect, the resonance frequency of the cantilevers is shifted because of a change in the magnetic biasing field. The biasing field, in turn, depends on the applied pressure or strain, respectively. With a view to the application as a reliable sensor, maximum sensitivity but minimum hysteresis in the biasing field/resonance frequency dependence is preferred. In this contribution, monomorph bending cantilevers fabricated using magnetostrictive Fe49Co49V2 and Metglas 2605SA1 are investigated regarding their applicability for future sensors. For this purpose, the biasing field-dependent polarization of the magnetostrictive materials and bending of the cantilevers are determined. Furthermore, a setup to magnetically bias the cantilevers and determine the bending resonance frequency is presented. Here, the resonance frequency is identified by measuring the impulse response employing a laser Doppler vibrometer. The measurement results reveal that cantilevers made of Fe49Co49V2 possess a distinct hysteretic behaviour at low magnetic biasing field magnitudes. This is ascribed to the polarization and bending hysteresis. Cantilevers fabricated using Metglas 2605SA1 feature a lower resonance frequency shift compared to cantilevers with Fe49Co49V2, which would result in a lower sensitivity of the sensor. However, their resonance frequency hysteresis is almost negligible.
YBCO superconducting ring resonators at millimeter-wave frequencies
Chorey, Christopher M.; Kong, Keon-Shik; Bhasin, Kul B.; Warner, J. D.; Itoh, Tatsuo
1991-01-01
Microstrip ring resonators operating at 35 GHz were fabricated from laser ablated YBCO films deposited on lanthanum aluminate substrates. They were measured over a range of temperatures and their performances compared to identical resonators made of evaporated gold. Below 60 Kelvin the superconducting strip performed better than the gold, reaching an unloaded Q approximately 1.5 times that of gold at 25 K. A shift in the resonant frequency follows the form predicted by the London equations. The Phenomenological Loss Equivalence Method is applied to the ring resonator and the theoretically calculated Q values are compared to the experimental results.
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...
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.
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.
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
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.
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.
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)
Design of tunable GHz-frequency optomechanical crystal resonators
Pfeifer, Hannes; Zang, Leyun; Painter, Oskar
2016-01-01
We present a silicon optomechanical nanobeam design with a dynamically tunable acoustic mode at 10.2 GHz. The resonance frequency can be shifted by 90 kHz/V^2 with an on-chip capacitor that was optimized to exert forces up to 1 $\\mu$N at 10 V operation voltage. Optical resonance frequencies around 190 THz with Q factors up to $2.2 \\times 10^6$ place the structure in the well-resolved sideband regime with vacuum optomechanical coupling rates up to $g_0/2\\pi = 353$ kHz. Tuning can be used, for instance, to overcome variation in the device-to-device acoustic resonance frequency due to fabrication errors, paving the way for optomechanical circuits consisting of arrays of optomechanical cavities.
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.
Circularly split-ring-resonator-based frequency-reconfigurable antenna
Rahman, M. A.; Faruque, M. R. I.; Islam, M. T.
2017-01-01
In this paper, an antenna with frequency configurability in light of a circularly split-ring resonator (CSRR) is introduced. The proposed reconfigurable monopole antenna consists of a microstrip-fed hook-shaped structure and a CSRR having single reconfigurable split only. A new band of radiation unlike the band radiated from monopole only is observed due to magnetic coupling between the CSRR and the monopole antenna. The resonance frequency of the CSRR can be arbitrarily chosen by varying the dimension and relative position of its gap with the monopole, which leads the antenna to become reconfigurable one. By using a single switch with perfect electric conductor at the gap of CSRR cell, the effect of CSRR can be deactivated and, hence, it is possible to suppress the corresponding resonance, resulting in a frequency-reconfigurable antenna. Commercially available Computer Simulation Technology microwave studio based on finite integration technique was adopted throughout the study.
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.
Relationship among resonant frequencies of Sierpinski multiband fractal antennas
Directory of Open Access Journals (Sweden)
Gonzalez-Rangel Ivan R.
2017-01-01
Full Text Available In this paper, the relationships between the different resonance frequencies of Sierpinski fractal antennas of four-iterations are studied. In particular, Sierpinski fractal antennas with operating frequencies of the initial triangle of 250 MHz, 350 MHz and 530 MHz were designed and built. The antennas are made of copper tablets with bakelite substrate. The performance of the designed antennas is measured in terms of return losses. The return losses are obtained experimentally with a “RFX” system that measures antenna parameters in conjunction with a network analyzer. These results are compared with numerical simulations of commercial finite-element program that analyzes high frequency electromagnetic structures “HFSS”. Experimental and simulation results show that there is approximately a factor of 2 between the resonance frequencies of the first and second iterations and the second and third iterations.
An ultra-broadband low-frequency magnetic resonance system
Mandal, S.; Utsuzawa, S.; Cory, D. G.; Hürlimann, M.; Poitzsch, M.; Song, Y.-Q.
2014-05-01
MR probes commonly employ resonant circuits for efficient RF transmission and low-noise reception. These circuits are narrow-band analog devices that are inflexible for broadband and multi-frequency operation at low Larmor frequencies. We have addressed this issue by developing an ultra-broadband MR probe that operates in the 0.1-3 MHz frequency range without using conventional resonant circuits for either transmission or reception. This “non-resonant” approach significantly simplifies the probe circuit and allows robust operation without probe tuning while retaining efficient power transmission and low-noise reception. We also demonstrate the utility of the technique through a variety of NMR and NQR experiments in this frequency range.
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.
Dual-frequency resonance-tracking atomic force microscopy
Rodriguez, Brian J.; Callahan, Clint; Kalinin, Sergei V.; Proksch, Roger
2007-11-01
A dual-excitation method for resonant-frequency tracking in scanning probe microscopy based on amplitude detection is developed. This method allows the cantilever to be operated at or near resonance for techniques where standard phase locked loops are not possible. This includes techniques with non-acoustic driving where the phase of the driving force is frequency and/or position dependent. An example of the latter is piezoresponse force microscopy (PFM), where the resonant frequency of the cantilever is strongly dependent on the contact stiffness of the tip-surface junction and the local mechanical properties, but the spatial variability of the drive phase rules out the use of a phase locked loop. Combined with high-voltage switching and imaging, dual-frequency, resonance-tracking PFM allows reliable studies of electromechanical and elastic properties and polarization dynamics in a broad range of inorganic and biological systems, and is illustrated using lead zirconate-titanate, rat tail collagen, and native and switched ferroelectric domains in lithium niobate.
Dual-frequency resonance-tracking atomic force microscopy
Energy Technology Data Exchange (ETDEWEB)
Rodriguez, Brian J [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Callahan, Clint [Asylum Research, Santa Barbara, CA 93117 (United States); Kalinin, Sergei V [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Proksch, Roger [Asylum Research, Santa Barbara, CA 93117 (United States)
2007-11-28
A dual-excitation method for resonant-frequency tracking in scanning probe microscopy based on amplitude detection is developed. This method allows the cantilever to be operated at or near resonance for techniques where standard phase locked loops are not possible. This includes techniques with non-acoustic driving where the phase of the driving force is frequency and/or position dependent. An example of the latter is piezoresponse force microscopy (PFM), where the resonant frequency of the cantilever is strongly dependent on the contact stiffness of the tip-surface junction and the local mechanical properties, but the spatial variability of the drive phase rules out the use of a phase locked loop. Combined with high-voltage switching and imaging, dual-frequency, resonance-tracking PFM allows reliable studies of electromechanical and elastic properties and polarization dynamics in a broad range of inorganic and biological systems, and is illustrated using lead zirconate-titanate, rat tail collagen, and native and switched ferroelectric domains in lithium niobate.
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.
Wide Frequency Band Active Damping Strategy for DFIG System High Frequency Resonance
DEFF Research Database (Denmark)
Song, Yipeng; Blaabjerg, Frede
2016-01-01
As a popular renewable power generation solution, the Doubly Fed Induction Generator (DFIG) based wind power system may suffer from High Frequency Resonance (HFR) caused by the impedance interaction between the DFIG system and the parallel compensated weak network. A wide frequency band active...... damping strategy for DFIG system HFR, including a high-pass filter and a virtual resistance, is proposed in this paper. The advantages of this active damping strategy are, 1) no resonance frequency detection unit is required, thus the control complexity can be decreased; 2) no active damping parameters...
Band Width of Acoustic Resonance Frequency Relatively Natural Frequency of Fuel Rod Vibration
Energy Technology Data Exchange (ETDEWEB)
Proskuryakov, Konstantin Nicolaevich; Moukhine, V.S.; Novikov, K.S.; Galivets, E.Yu. [MPEI - TU, 14, Krasnokazarmennaya str., Moscow, 111250 (Russian Federation)
2009-06-15
In flow induced vibrations the fluid flow is the energy source that causes vibration. Acoustic resonance in piping may lead to severe problems due to over-stressing of components or significant losses of efficiency. Steady oscillatory flow in NPP primary loop can be induced by the pulsating flow introduced by reactor circulating pump or may be set up by self-excitation. Dynamic forces generated by the turbulent flow of coolant in reactor cores cause fuel rods (FR) and fuel assembly (FA) to vibrate. Flow-induced FR and FA vibrations can generally be broken into three groups: large amplitude 'resonance type' vibrations, which can cause immediate rod failure or severe damage to the rod and its support structure, middle amplitude 'within bandwidth of resonance frequency type' vibrations responsible for more gradual wear and fatigue at the contact surface between the fuel cladding and rod support and small amplitude vibrations, 'out of bandwidth of resonance frequency type' responsible for permissible wear and fatigue at the contact surface between the fuel cladding and rod support. Ultimately, these vibration types can result in a cladding breach, and therefore must be accounted for in the thermal hydraulic design of FR and FA and reactor internals. In paper the technique of definition of quality factor (Q) of acoustic contour of the coolant is presented. The value of Q defines a range of frequencies of acoustic fluctuations of the coolant within which the resonance of oscillations of the structure and the coolant is realized. Method of evaluation of so called band width (BW) of acoustic resonance frequency is worked out and presented in the paper. BW characterises the range of the frequency of coolant pressure oscillations within which the frequency of coolant pressure oscillations matches the fuel assembly's natural frequency of vibration (its resonance frequency). Paper show the way of detuning acoustic resonance from natural
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.
PT -symmetric spectral singularity and negative-frequency resonance
Pendharker, Sarang; Guo, Yu; Khosravi, Farhad; Jacob, Zubin
2017-03-01
Vacuum consists of a bath of balanced and symmetric positive- and negative-frequency fluctuations. Media in relative motion or accelerated observers can break this symmetry and preferentially amplify negative-frequency modes as in quantum Cherenkov radiation and Unruh radiation. Here, we show the existence of a universal negative-frequency-momentum mirror symmetry in the relativistic Lorentzian transformation for electromagnetic waves. We show the connection of our discovered symmetry to parity-time (PT ) symmetry in moving media and the resulting spectral singularity in vacuum fluctuation-related effects. We prove that this spectral singularity can occur in the case of two metallic plates in relative motion interacting through positive- and negative-frequency plasmonic fluctuations (negative-frequency resonance). Our work paves the way for understanding the role of PT -symmetric spectral singularities in amplifying fluctuations and motivates the search for PT symmetry in novel photonic systems.
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.
Optical Kerr Frequency Comb Generation in Overmoded Resonators
Matsko, A B; Liang, W; Ilchenko, V S; Seidel, D; Maleki, L
2012-01-01
We show that scattering-based interaction among nearly degenerate optical modes is the key factor in low threshold generation of Kerr frequency combs in nonlinear optical resonators possessing small group velocity dispersion (GVD). The mode interaction is capable of producing drastic change in the local GVD, resulting in either a significant reduction or increase of the oscillation threshold. It is also responsible for the majority of observed combs in resonators characterized with large normal GVD. We present results of our numerical simulations as well as supporting experimental data.
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.
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.
Effect of geometry in frequency response modeling of nanomechanical resonators
Esfahani, M. Nasr; Yilmaz, M.; Sonne, M. R.; Hattel, J. H.; Alaca, B. Erdem
2016-06-01
The trend towards nanomechanical resonator sensors with increasing sensitivity raises the need to address challenges encountered in the modeling of their mechanical behavior. Selecting the best approach in mechanical response modeling amongst the various potential computational solid mechanics methods is subject to controversy. A guideline for the selection of the appropriate approach for a specific set of geometry and mechanical properties is needed. In this study, geometrical limitations 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-Born technique 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 on the order of 50 % is reported for high-aspect ratio resonators.
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.
Frequency resonance effect of neurons under low-frequency weak magnetic field
Azanza, María J.; del Moral, A.; Pérez Bruzón, R. N.
2007-03-01
We report on the frequency resonance effect observed in single neurons of mollusc Helix brain under low-frequency B=1 mT magnetic fields of frequency f M=0.1-80 Hz. The dependence of the firing frequency f with f M decreases as a Lorentzian, centered about the spontaneous, f0 one ("window effect"). An explanation is provided based on the superdiamagnetism and Ca 2+ coulomb explosion model, supplemented by the Ca 2+ kinetics towards the Ca 2+-dependent K + channels, opening them. The Ca 2+ ion diffusion time is obtained.
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.
Assessment of Stability of Craniofacial Implants by Resonant Frequency Analysis.
Ivanjac, Filip; Konstantinović, Vitomir S; Lazić, Vojkan; Dordević, Igor; Ihde, Stefan
2016-03-01
Implant stability is a principal precondition for the success of implant therapy. Extraoral implants (EO) are mainly used for anchoring of maxillofacial epithesis. However, assessment of implant stability is mostly based on principles derived from oral implants. The aim of this study was to investigate clinical stability of EO craniofacial disk implants (single, double, and triple) by resonance frequency analysis at different stages of the bone's healing. Twenty patients with orbital (11), nasal (5), and auricular (4) defects with 50 EO implants placed for epithesis anchorage were included. Implant stability was measured 3 times; after implant placement, at 3 months and at least after 6 months. A significant increase in implant stability values was noted between all of the measurements, except for triple-disk implants between third and sixth months, and screw implants between 0 and third months. Disk implants showed lower implant stability quotient (ISQ) values compared with screw implants. Triple-disk implants showed better stability compared with single and double-disk implants. Based on resonance frequency analysis values, disk implants could be safely loaded when their ISQ values are 38 (single disks), 47 (double disks), and 48 (triple disks). According to resonance frequency analysis, disk implant stability increased over time, which showed good osseointegration and increasing mineralization. Although EO screw implants showed higher ISQ values than disk implants, disk-type implants can be safely loaded even if lower values of stability are measured.
Low-frequency nuclear quadrupole resonance with a dc SQUID
Energy Technology Data Exchange (ETDEWEB)
Chang, J.W.
1991-07-01
Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.
Low-frequency nuclear quadrupole resonance with a dc SQUID
Chang, J. W.
1991-07-01
Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region are traditionally difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a RF field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter.
Effect of off-frequency sampling in magnetic resonance elastography.
Johnson, Curtis L; Chen, Danchin D; Olivero, William C; Sutton, Bradley P; Georgiadis, John G
2012-02-01
In magnetic resonance elastography (MRE), shear waves at a certain frequency are encoded through bipolar gradients that switch polarity at a controlled encoding frequency and are offset in time to capture wave propagation using a controlled sampling frequency. In brain MRE, there is a possibility that the mechanical actuation frequency is different from the vibration frequency, leading to a mismatch with encoding and sampling frequencies. This mismatch can occur in brain MRE from causes both extrinsic and intrinsic to the brain, such as scanner bed vibrations or active damping in the head. The purpose of this work was to investigate how frequency mismatch can affect MRE shear stiffness measurements. Experiments were performed on a dual-medium agarose gel phantom, and the results were compared with numerical simulations to quantify these effects. It is known that off-frequency encoding alone results in a scaling of wave amplitude, and it is shown here that off-frequency sampling can result in two main effects: (1) errors in the overall shear stiffness estimate of the material on the global scale and (2) local variations appearing as stiffer and softer structures in the material. For small differences in frequency, it was found that measured global stiffness of the brain could theoretically vary by up to 12.5% relative to actual stiffness with local variations of up to 3.7% of the mean stiffness. It was demonstrated that performing MRE experiments at a frequency other than that of tissue vibration can lead to artifacts in the MRE stiffness images, and this mismatch could explain some of the large-scale scatter of stiffness data or lack of repeatability reported in the brain MRE literature.
Miller, Lindsay Margaret
hundred milliwatts and are falling steadily as improvements are made, it is feasible to use energy harvesting to power WSNs. This research begins by presenting the results of a thorough survey of ambient vibrations in the machine room of a large campus building, which found that ambient vibrations are low frequency, low amplitude, time varying, and multi-frequency. The modeling and design of fixed-frequency micro scale energy harvesters are then presented. The model is able to take into account rotational inertia of the harvester's proof mass and it accepts arbitrary measured acceleration input, calculating the energy harvester's voltage as an output. The fabrication of the micro electromechanical system (MEMS) energy harvesters is discussed and results of the devices harvesting energy from ambient vibrations are presented. The harvesters had resonance frequencies ranging from 31 - 232 Hz, which was the lowest reported in literature for a MEMS device, and produced 24 pW/g2 - 10 nW/g2 of harvested power from ambient vibrations. A novel method for frequency modification of the released harvester devices using a dispenser printed mass is then presented, demonstrating a frequency shift of 20 Hz. Optimization of the MEMS energy harvester connected to a resistive load is then presented, finding that the harvested power output can be increased to several microwatts with the optimized design as long as the driving frequency matches the harvester's resonance frequency. A framework is then presented to allow a similar optimization to be conducted with the harvester connected to a synchronously switched pre-bias circuit. With the realization that the optimized energy harvester only produces usable amounts of power if the resonance frequency and driving frequency match, which is an unrealistic situation in the case of ambient vibrations which change over time and are not always known a priori, an adaptable-frequency energy harvester was designed. The adaptable-frequency harvester
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.
Device for measurement of power and shape of radio frequency pulses in nuclear magnetic resonance
Pfeffer, M.; Řezníček, R.; Křišťan, P.; Štěpánková, H.
2012-05-01
A design of an instrument to measure the power and shape of radio frequency (RF) pulses operating in a broad frequency range is described. The device is capable of measuring the pulse power up to 500 W of both CW and extremely short (˜1 μs) RF pulses of arbitrary period. The pulse envelope can be observed on a logarithmic scale on a corresponding instrument output using an inexpensive storage oscilloscope. The instrument consists of a coaxial measurement head, the RF processing circuits and an AD conversion and display unit. The whole device is based on widely available integrated circuits; thus, good reproducibility and adaptability of the design is ensured. Since the construction is intended to be used in particular (but not solely) in nuclear magnetic resonance spectroscopy, we found it useful to provide a demonstration of two typical usage scenarios. Other application fields may comprise magnetic resonance imaging, radar and laser technology, power amplifier testing, etc.
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.
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.
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.
Whispering gallery mode resonators for frequency metrology applications
Baumgartel, Lukas
This dissertation describes an investigation into the use of whispering gallery mode (WGM) resonators for applications towards frequency reference and metrology. Laser stabilization and the measurement of optical frequencies have enabled myriad technologies of both academic and commercial interest. A technology which seems to span both motivations is optical atomic clocks. These devices are virtually unimaginable without the ultra stable lasers plus frequency measurement and down-conversion afforded by Fabry Perot (FP) cavities and model-locked laser combs, respectively. However, WGM resonators can potentially perform both of these tasks while having the distinct advantages of compactness and simplicity. This work represents progress towards understanding and mitigating the performance limitations of WGM cavities for such applications. A system for laser frequency stabilization to a the cavity via the Pound-Drever-Hall (PDH) method is described. While the laser lock itself is found to perform at the level of several parts in 1015, a variety of fundamental and technical mechanisms destabilize the WGM frequency itself. Owing to the relatively large thermal expansion coefficients in optical crystals, environmental temperature drifts set the stability limit at time scales greater than the thermal relaxation time of the crystal. Uncompensated, these drifts pull WGM frequencies about 3 orders of magnitude more than they would in an FP cavity. Thus, two temperature compensation schemes are developed. An active scheme measures and stabilizes the mode volume temperature to the level of several nK, reducing the effective temperature coefficient of the resonator to 1.7x10-7 K-1; simulations suggest that the value could eventually be as low as 3.5x10-8 K-1, on par with the aforementioned FP cavities. A second, passive scheme is also described, which employs a heterogeneous resonator structure that capitalizes on the thermo-mechanical properties of one material and the optical
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
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.
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.
Wideband bioimpedance meter with the adaptive selection of frequency grid
V. S. Mosiychuk; G. V. Timoshenko; O. B. Sharpan
2014-01-01
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. Develope...
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.
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.
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...
Frequency Adaptability and Waveform Design for OFDM Radar Space-Time Adaptive Processing
Energy Technology Data Exchange (ETDEWEB)
Sen, Satyabrata [ORNL; Glover, Charles Wayne [ORNL
2012-01-01
We propose an adaptive waveform design technique for an orthogonal frequency division multiplexing (OFDM) radar signal employing a space-time adaptive processing (STAP) technique. We observe that there are inherent variabilities of the target and interference responses in the frequency domain. Therefore, the use of an OFDM signal can not only increase the frequency diversity of our system, but also improve the target detectability by adaptively modifying the OFDM coefficients in order to exploit the frequency-variabilities of the scenario. First, we formulate a realistic OFDM-STAP measurement model considering the sparse nature of the target and interference spectra in the spatio-temporal domain. Then, we show that the optimal STAP-filter weight-vector is equal to the generalized eigenvector corresponding to the minimum generalized eigenvalue of the interference and target covariance matrices. With numerical examples we demonstrate that the resultant OFDM-STAP filter-weights are adaptable to the frequency-variabilities of the target and interference responses, in addition to the spatio-temporal variabilities. Hence, by better utilizing the frequency variabilities, we propose an adaptive OFDM-waveform design technique, and consequently gain a significant amount of STAP-performance improvement.
Frequency resonance effect of neurons under low-frequency weak magnetic field
Energy Technology Data Exchange (ETDEWEB)
Azanza, Maria J. [Laboratorio de Magnetobiologia, Facultad de Medicina, Universidad de Zaragoza, 50009 Zaragoza (Spain)]. E-mail: mjazanza@unizar.es; Moral, A. del [Laboratorio de Magnetismo de Solidos, DFMC and ICMA, Universidad de Zaragoza and CSIC, 50009 Zaragoza (Spain); Perez Bruzon, R.N. [Laboratorio de Magnetobiologia, Facultad de Medicina, Universidad de Zaragoza, 50009 Zaragoza (Spain)
2007-03-15
We report on the frequency resonance effect observed in single neurons of mollusc Helix brain under low-frequency B=1 mT magnetic fields of frequency f{sub M} =0.1-80 Hz. The dependence of the firing frequency f with f{sub M} decreases as a Lorentzian, centered about the spontaneous, f {sub 0} one ('window effect'). An explanation is provided based on the superdiamagnetism and Ca{sup 2+} coulomb explosion model, supplemented by the Ca{sup 2+} kinetics towards the Ca{sup 2+}-dependent K{sup +} channels, opening them. The Ca{sup 2+} ion diffusion time is obtained.
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.
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.
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.
Aguirre-Ollinger, Gabriel
2015-01-01
In this article, we analyze a novel strategy for assisting the lower extremities based on adaptive frequency oscillators. Our aim is to use the control algorithm presented here as a building block for the control of powered lower-limb exoskeletons. The algorithm assists cyclic movements of the human extremities by synchronizing actuator torques with the estimated net torque exerted by the muscles. Synchronization is produced by a nonlinear dynamical system combining an adaptive frequency oscillator with a form of adaptive Fourier analysis. The system extracts, in real time, the fundamental frequency component of the net muscle torque acting on a specific joint. Said component, nearly sinusoidal in shape, is the basis for the assistive torque waveform delivered by the exoskeleton. The action of the exoskeleton can be interpreted as a virtual reduction in the mechanical impedance of the leg. We studied the ability of human subjects to adapt their muscle activation to the assistive torque. Ten subjects swung their extended leg while coupled to a stationary hip joint exoskeleton. The experiment yielded a significant decrease, with respect to unassisted movement, of the activation levels of an agonist/antagonist pair of muscles controlling the hip joint's motion, which suggests the exoskeleton control has potential for assisting human gait. A moderate increase in swing frequency was observed as well. We theorize that the increase in frequency can be explained by the impedance model of the assisted leg. Per this model, subjects adjust their swing frequency in order to control the amount of reduction in net muscle torque.
Lin, Jian; Liu, Jiaming; Zhang, Hao; Li, Wenxiu; Zhao, Lu; Jin, Junjie; Huang, Anping; Zhang, Xiaofu; Xiao, Zhisong
2016-12-01
Rigorous expressions of resonant frequency shift (RFS) in anomalous dispersion enhanced resonant optical gyroscopes (ADEROGs) are deduced without making approximation, which provides a precise theoretical guidance to achieve ultra-sensitive ADEROGs. A refractive index related modification factor is introduced when considering special theory of relativity (STR). We demonstrate that the RFS will not be ”infinitely large” by using critical anomalous dispersion (CAD) and negative modification does not exist, which make the mechanism of anomalous dispersion enhancement clear and coherent. Although step change of RFS will happen when the anomalous dispersion condition varies, the amplification of RFS is limited by attainable variation of refractive index in practice. Moreover, it is shown that the properties of anomalous dispersion will influence not only the amplification of RFS, but also the detection range of ADEROGs.
Adaptation behavior of skilled infant bouncers to different spring frequencies
Olinda Habib Perez; Coren Walters-Stewart; Robertson, D.G. E; Natalie Baddour; Heidi Sveistrup
2015-01-01
Infants explore their environments through repetitive movements that are constrained or facilitated by the environmental context. In this study, we evaluated how skilled bouncers adapted to bouncing in systems with four different spring conditions (natural frequencies of 0.9, 1.15, 1.27 and 1.56 Hz). Trunk kinematics and vertical ground reaction forces (VGRFs) were recorded from three pre-walking infants (mean age 10.6 ±0.9 months). Bounce frequency, trunk displacement, peak VGRF, percent of ...
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...
Adaptation behavior of skilled infant bouncers to different spring frequencies
Directory of Open Access Journals (Sweden)
Olinda Habib Perez
2015-05-01
Full Text Available Infants explore their environments through repetitive movements that are constrained or facilitated by the environmental context. In this study, we evaluated how skilled bouncers adapted to bouncing in systems with four different spring conditions (natural frequencies of 0.9, 1.15, 1.27 and 1.56 Hz. Trunk kinematics and vertical ground reaction forces (VGRFs were recorded from three pre-walking infants (mean age 10.6 ±0.9 months. Bounce frequency, trunk displacement, peak VGRF, percent of time on the ground and time to peak force as a function of time on the ground were analyzed. In addition, infant bounce frequencies were compared to measured oscillations of an inert mass equivalent to each infant’s mass. All infants bounced above the natural frequency of the spring system in all conditions suggesting that they did not behave solely like mass-spring systems. Infants produced asymmetrical VGRF loading patterns suggesting that a timing component, such as bounce frequency, was regulated. Skilled infants consistently increased their bounce frequency as their vertical trunk displacement decreased; however, the mode for regulating bounce frequency differed from infant to infant.
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.
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}...
Robust identification of local adaptation from allele frequencies.
Günther, Torsten; Coop, Graham
2013-09-01
Comparing allele frequencies among populations that differ in environment has long been a tool for detecting loci involved in local adaptation. However, such analyses are complicated by an imperfect knowledge of population allele frequencies and neutral correlations of allele frequencies among populations due to shared population history and gene flow. Here we develop a set of methods to robustly test for unusual allele frequency patterns and correlations between environmental variables and allele frequencies while accounting for these complications based on a Bayesian model previously implemented in the software Bayenv. Using this model, we calculate a set of "standardized allele frequencies" that allows investigators to apply tests of their choice to multiple populations while accounting for sampling and covariance due to population history. We illustrate this first by showing that these standardized frequencies can be used to detect nonparametric correlations with environmental variables; these correlations are also less prone to spurious results due to outlier populations. We then demonstrate how these standardized allele frequencies can be used to construct a test to detect SNPs that deviate strongly from neutral population structure. This test is conceptually related to FST and is shown to be more powerful, as we account for population history. We also extend the model to next-generation sequencing of population pools-a cost-efficient way to estimate population allele frequencies, but one that introduces an additional level of sampling noise. The utility of these methods is demonstrated in simulations and by reanalyzing human SNP data from the Human Genome Diversity Panel populations and pooled next-generation sequencing data from Atlantic herring. An implementation of our method is available from http://gcbias.org.
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.
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.
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.
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.
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.
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...
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.
Tkach, Igor; Sicoli, Giuseppe; Höbartner, Claudia; Bennati, Marina
2011-04-01
We present a dual-mode resonator operating at/near 94 GHz (W-band) microwave frequencies and supporting two microwave modes with the same field polarization at the sample position. Numerical analysis shows that the frequencies of both modes as well as their frequency separation can be tuned in a broad range up to GHz. The resonator was constructed to perform pulsed ELDOR experiments with a variable separation of "pump" and "detection" frequencies up to Δ ν = 350 MHz. To examine its performance, test ESE/PELDOR experiments were performed on a representative biradical system.
Leung, L S; Yu, H W
1998-03-01
Sinusoidal currents of various frequencies were injected into hippocampal CA1 neurons in vitro, and the membrane potential responses were analyzed by cross power spectral analysis. Sinusoidal currents induced a maximal (resonant) response at a theta frequency (3-10 Hz) in slightly depolarized neurons. As predicted by linear systems theory, the resonant frequency was about the same as the natural (spontaneous) oscillation frequency. However, in some cases, the resonant frequency was higher than the spontaneous oscillation frequency, or resonance was found in the absence of spontaneous oscillations. The sharpness of the resonance (Q), measured by the peak frequency divided by the half-peak power bandwidth, increased from a mean of 0.44 at rest to 0.83 during a mean depolarization of 6.5 mV. The phase of the driven oscillations changed most rapidly near the resonant frequency, and it shifted about 90 degrees over the half-peak bandwidth of 8.4 Hz. Similar results were found using a sinusoidal function of slowly changing frequency as the input. Sinusoidal currents of peak-to-peak intensity of >100 pA may evoke nonlinear responses characterized by second and higher harmonics. The theta-frequency resonance in hippocampal neurons in vitro suggests that the same voltage-dependent phenomenon may be important in enhancing a theta-frequency response when hippocampal neurons are driven by medial septal or other inputs in vivo.
Frequency and Spatial Selectivity in Nuclear Magnetic Resonance Spectroscopy.
Friedrich, Jan O.
1988-12-01
Available from UMI in association with The British Library. Requires signed TDF. The techniques presented in this thesis are concerned with the high resolution nuclear magnetic resonance spectra of liquids. A selective pulse, shaped according to the first half of a Gaussian curve, is developed; it gives a very narrow absorption-mode excitation profile. This characteristics is used in developing selective coherence transfer experiments in which an individual transition is irradiated by the selective pulse followed by irradiation with an intense non-selective pulse. By stepping the irradiation frequency of the selective pulse along in small increments, this experiment produces results similar to conventional two-dimensional homonuclear correlation spectroscopy. Such a method allows selected spectral regions of a conventional two-dimensional spectrum to be examined under higher resolution while avoiding the restrictions imposed by the sampling theorem. The technique is also extended to a third frequency dimension by irradiating two transitions simultaneously before applying a non-selective pulse which yields correlations between three coupled nuclei. The remainder of this thesis introduces a spatial localisation method based on a "straddle coil": two parallel coaxial surface coils, one on each side of the sample and supplied with radiofrequency pulses of opposite phase. This configuration can be used for spatial localisation experiments by applying a sequence of equal and opposite prepulses before acquiring the signal. The prepulses saturate the nuclear spins in all sample regions except the sensitive volume close to the median plane where the radiofrequency fields from the two coils cancel. Pulse sequences are proposed that are insensitive to radiofrequency offset over an appreciable range. The location of the sensitive volume can be tracked across the sample in the axial dimension by changing the ratio of the radiofrequency currents in the two coils.
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.
Droit, C; Martin, G; Ballandras, S; Friedt, J-M
2010-05-01
We demonstrate the wireless conversion of frequency modulation to amplitude modulation by radio frequency resonators as means of accurately determining the resonance frequency of passive acoustoelectronic sensors. The emitted frequency modulated radio frequency pulses are generated by a pulsed radar for probing a surface acoustic wave based sensor. The sharp sign transition of the amplitude modulated received signal provides a signal on which a feedback loop is locked to monitor the resonance signal. The strategy is demonstrated using a full software implementation on a generic hardware, resulting in 2 Hz resolution at 1 s integration time limited by the proportional feedback loop.
The Tracking Resonance Frequency Method for Photoacoustic Measurements Based on the Phase Response
Suchenek, Mariusz
2017-04-01
One of the major issues in the use of the resonant photoacoustic cell is the resonance frequency of the cell. The frequency is not stable, and its changes depend mostly on temperature and gas mixture. This paper presents a new method for tracking resonance frequency, where both the amplitude and phase are calculated from the input samples. The stimulating frequency can be adjusted to the resonance frequency of the cell based on the phase. This method was implemented using a digital measurement system with an analog to digital converter, field programmable gate array (FPGA) and a microcontroller. The resonance frequency was changed by the injection of carbon dioxide into the cell. A theoretical description and experimental results are also presented.
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.
Energy Technology Data Exchange (ETDEWEB)
Seemann, K., E-mail: klaus.seemann@kit.edu; Leiste, H.; Krüger, K.
2013-11-15
Soft ferromagnetic Fe-Co-Hf-N films, produced by reactive r.f. magnetron sputtering, are useful to study the ferromagnetic resonance (FMR) by means of frequency domain permeability measurements up to the GHz range. Films with the composition Fe{sub 33}Co{sub 43}Hf{sub 10}N{sub 14} exhibit a saturation polarisation J{sub s} of around 1.35 T. They are consequently considered as being uniformly magnetised due to an in-plane uniaxial anisotropy of approximately μ{sub 0}H{sub u}≈4.5 m T after annealing them, e.g., at 400 °C in a static magnetic field for 1 h. Being exposed to a high-frequency field, the precession of magnetic moments leads to a marked frequency-dependent permeability with a sharp Lorentzian shaped imaginary part at around 2.33 GHz (natural resonance peak), which is in a very good agreement with the modified Landau–Lifschitz–Gilbert (LLG) differential equation. A slightly increased FMR frequency and a clear increase in the resonance line broadening due to an increase of the exciting high-frequency power (1–25.1 mW), considered as an additional perturbation of the precessing system of magnetic moments, could be discovered. By solving the homogenous LLG differential equation with respect to the in-plane uniaxial anisotropy, it was revealed that the high-frequency field perturbation impacts the resonance peak position f{sub FMR} and resonance line broadening Δf{sub FMR} characterised by a completed damping parameter α=α{sub eff}+Δα. Adapted from this result, the increase in f{sub FMR} and decrease in lifetime of the excited level of magnetic moments associated with Δf{sub FMR}, similar to a spin-½ particle in a static magnetic field, was theoretically elaborated as well as compared with experimental data. - Highlights: • Impact on the resonance frequency and resonance line by the high-frequency power. • Theoretic approach by solving the LLG differential equation. • Experimental verification and magnon processes. • Theoretical and
Analysis of Middle Frequency Resonance in DFIG System Considering Phase Locked Loop
DEFF Research Database (Denmark)
Song, Yipeng; Blaabjerg, Frede
2017-01-01
As the wind power technology develops, the Doubly Fed Induction Generator (DFIG) based wind power system, when connected to a weak network with large impedance, may suffer resonances, i.e., Sub- Synchronous Resonance (SSR) or High Frequency Resonance (HFR) when connected to the series or parallel...
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....
Outphasing control of gallium nitride based very high frequency resonant converters
DEFF Research Database (Denmark)
Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.
2015-01-01
In this paper an outphasing modulation control method suitable for line regulation of very high frequency resonant converters is described. The pros and cons of several control methods suitable for very high frequency resonant converters are described and compared to outphasing modulation...
Analysis on the Behavior of Undamped and Unstable High Frequency Resonance in DFIG System
DEFF Research Database (Denmark)
Song, Yipeng; Blaabjerg, Frede
2017-01-01
As the wind power generation develops, the Doubly Fed Induction Generator (DFIG) based wind power system may suffer Sub Synchronous Resonance (SSR) and High Frequency Resonance (HFR) in the series and parallel compensated weak network. The principle and frequency of HFR have been discussed using ...
Zero field anti ferromagnetic resonance at optical frequencies in dilute magnetic system
Paul, Somnath; Sarkar, A.
2015-06-01
An experimental study of Antiferromagnetic resonance on Cobalt and Nickel oxide at room temperature has been undertaken. The zero field resonance frequency is detected in near infrared frequency regime. The measurement makes use of UV-VIS spectrophotometer. The overall results are found to be good and encouraging.
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.
Seemann, K.; Leiste, H.; Krüger, K.
2013-11-01
Soft ferromagnetic Fe-Co-Hf-N films, produced by reactive r.f. magnetron sputtering, are useful to study the ferromagnetic resonance (FMR) by means of frequency domain permeability measurements up to the GHz range. Films with the composition Fe33Co43Hf10N14 exhibit a saturation polarisation Js of around 1.35 T. They are consequently considered as being uniformly magnetised due to an in-plane uniaxial anisotropy of approximately μ0Hu≈4.5 m T after annealing them, e.g., at 400 °C in a static magnetic field for 1 h. Being exposed to a high-frequency field, the precession of magnetic moments leads to a marked frequency-dependent permeability with a sharp Lorentzian shaped imaginary part at around 2.33 GHz (natural resonance peak), which is in a very good agreement with the modified Landau-Lifschitz-Gilbert (LLG) differential equation. A slightly increased FMR frequency and a clear increase in the resonance line broadening due to an increase of the exciting high-frequency power (1-25.1 mW), considered as an additional perturbation of the precessing system of magnetic moments, could be discovered. By solving the homogenous LLG differential equation with respect to the in-plane uniaxial anisotropy, it was revealed that the high-frequency field perturbation impacts the resonance peak position fFMR and resonance line broadening ΔfFMR characterised by a completed damping parameter α=αeff+Δα. Adapted from this result, the increase in fFMR and decrease in lifetime of the excited level of magnetic moments associated with ΔfFMR, similar to a spin-½ particle in a static magnetic field, was theoretically elaborated as well as compared with experimental data.
Resonance of a Metal Drop under the Effect of Amplitude-Modulated High Frequency Magnetic Field
Guo, Jiahong; Lei, Zuosheng; Zhu, Hongda; Zhang, Lijie; Magnetic Hydrodynamics(Siamm) Team; Magnetic Mechanics; Engineering(Smse) Team
2016-11-01
The resonance of a sessile and a levitated drop under the effect of high frequency amplitude-modulated magnetic field (AMMF) is investigated experimentally and numerically. It is a new method to excite resonance of a metal drop, which is different from the case in the presence of a low-frequency magnetic field. The transient contour of the drop is obtained in the experiment and the simulation. The numerical results agree with the experimental results fairly well. At a given frequency and magnetic flux density of the high frequency AMMF, the edge deformations of the drop with an azimuthal wave numbers were excited. A stability diagram of the shape oscillation of the drop and its resonance frequency spectrum are obtained by analysis of the experimental and the numerical data. The results show that the resonance of the drop has a typical character of parametric resonance. The National Natural Science Foundation of China (No. 51274237 and 11372174).
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).
Hanson, D.; Waters, T. P.; Thompson, D. J.; Randall, R. B.; Ford, R. A. J.
2007-01-01
Finite element model updating traditionally makes use of both resonance and modeshape information. The mode shape information can also be obtained from anti-resonance frequencies, as has been suggested by a number of researchers in recent years. Anti-resonance frequencies have the advantage over mode shapes that they can be much more accurately identified from measured frequency response functions. Moreover, anti-resonance frequencies can, in principle, be estimated from output-only measurements on operating machinery. The motivation behind this paper is to explore whether the availability of anti-resonances from such output-only techniques would add genuinely new information to the model updating process, which is not already available from using only resonance frequencies. This investigation employs two-degree-of-freedom models of a rigid beam supported on two springs. It includes an assessment of the contribution made to the overall anti-resonance sensitivity by the mode shape components, and also considers model updating through Monte Carlo simulations, experimental verification of the simulation results, and application to a practical mechanical system, in this case a petrol generator set. Analytical expressions are derived for the sensitivity of anti-resonance frequencies to updating parameters such as the ratio of spring stiffnesses, the position of the centre of gravity, and the beam's radius of gyration. These anti-resonance sensitivities are written in terms of natural frequency and mode shape sensitivities so their relative contributions can be assessed. It is found that the contribution made by the mode shape sensitivity varies considerably depending on the value of the parameters, contributing no new information for significant combinations of parameter values. The Monte Carlo simulations compare the performance of the update achieved when using information from: the resonances only; the resonances and either anti-resonance; and the resonances and both
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.
Insertion torque, resonance frequency, and removal torque analysis of microimplants.
Tseng, Yu-Chuan; Ting, Chun-Chan; Du, Je-Kang; Chen, Chun-Ming; Wu, Ju-Hui; Chen, Hong-Sen
2016-09-01
This study aimed to compare the insertion torque (IT), resonance frequency (RF), and removal torque (RT) among three microimplant brands. Thirty microimplants of the three brands were used as follows: Type A (titanium alloy, 1.5-mm × 8-mm), Type B (stainless steel, 1.5-mm × 8-mm), and Type C (titanium alloy, 1.5-mm × 9-mm). A synthetic bone with a 2-mm cortical bone and bone marrow was used. Each microimplant was inserted into the synthetic bone, without predrilling, to a 7 mm depth. The IT, RF, and RT were measured in both vertical and horizontal directions. One-way analysis of variance and Spearman's rank correlation coefficient tests were used for intergroup and intragroup comparisons, respectively. In the vertical test, the ITs of Type C (7.8 Ncm) and Type B (7.5 Ncm) were significantly higher than that of Type A (4.4 Ncm). The RFs of Type C (11.5 kHz) and Type A (10.2 kHz) were significantly higher than that of Type B (7.5 kHz). Type C (7.4 Ncm) and Type B (7.3 Ncm) had significantly higher RTs than did Type A (4.1 Ncm). In the horizontal test, both the ITs and RTs were significantly higher for Type C, compared with Type A. No significant differences were found among the groups, and the study hypothesis was accepted. Type A had the lowest inner/outer diameter ratio and widest apical facing angle, engendering the lowest IT and highest RF values. However, no significant correlations in the IT, RF, and RT were observed among the three groups.
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.
Experimental Validation of a Theory for a Variable Resonant Frequency Wave Energy Converter (VRFWEC)
Park, Minok; Virey, Louis; Chen, Zhongfei; Mäkiharju, Simo
2016-11-01
A point absorber wave energy converter designed to adapt to changes in wave frequency and be highly resilient to harsh conditions, was tested in a wave tank for wave periods from 0.8 s to 2.5 s. The VRFWEC consists of a closed cylindrical floater containing an internal mass moving vertically and connected to the floater through a spring system. The internal mass and equivalent spring constant are adjustable and enable to match the resonance frequency of the device to the exciting wave frequency, hence optimizing the performance. In a full scale device, a Permanent Magnet Linear Generator will convert the relative motion between the internal mass and the floater into electricity. For a PMLG as described in Yeung et al. (OMAE2012), the electromagnetic force proved to cause dominantly linear damping. Thus, for the present preliminary study it was possible to replace the generator with a linear damper. While the full scale device with 2.2 m diameter is expected to generate O(50 kW), the prototype could generate O(1 W). For the initial experiments the prototype was restricted to heave motion and data compared to predictions from a newly developed theoretical model (Chen, 2016).
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.
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
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...
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.
Fan, N. Q.; Clarke, John
1991-06-01
A sensitive spectrometer, based on a dc superconducting quantum interference device, for the direct detection of low-frequency pulsed nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR), is described. The frequency response extends from about 10 to 200 kHz, and the recovery time after the magnetic pulse is removed is typically 50 μs. As examples, NMR spectra are shown from Pt and Cu metal powders in a magnetic field of 6 mT, and NQR spectra are shown from 2D in a tunneling methyl group and 14N in NH4ClO4.
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.
Frequency Adaptive Repetitive Control of Grid-Tied Three-Phase PV iInverters
DEFF Research Database (Denmark)
Zhou, Keliang; Yang, Yongheng; Blaabjerg, Frede
2016-01-01
in the presence of practical time-varying grid frequency. This paper explores frequency adaptive repetitive control strategy for grid-interfaced converters, which employs fractional delay filter to adapt to the change of grid frequency. Case studies with experimental results of three-phase grid-connected...... converter systems are provided to verify the proposed controller....
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.
On the application of radio frequency voltages to ion traps via helical resonators
Siverns, J D; Weidt, S; Hensinger, W K
2011-01-01
Ions confined using a Paul trap require a stable, high voltage and low noise radio frequency (RF) potential. We present a guide for the design and construction of a helical coil resonator for a desired frequency that maximises the quality factor for a set of experimental constraints. We provide an in-depth analysis of the system formed from a shielded helical coil and an ion trap by treating the system as a lumped element model. This allows us to predict the resonant frequency and quality factor in terms of the physical parameters of the resonator and the properties of the ion trap. We also compare theoretical predictions with experimental data for different resonators, and predict the voltage applied to the ion trap as a function of the Q-factor, input power and the properties of the resonant circuit.
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.
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...
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.
Pietkiewicz, A.; Tollik, D.; Klaassens, J. B.
1989-08-01
A simple small-signal low-frequency model of an idealized series resonant converter employing peak capacitor voltage prediction and switching frequency control is proposed. Two different versions of the model describe all possible conversion modes. It is found that step down modes offer better dynamic characteristics over most important network functions than do the step-up modes. The dynamical model of the series resonant converter with peak capacitor voltage prediction and switching frequency programming is much simpler than such popular control stategies as frequency VCO (voltage controlled oscillators) based control, or diode conduction angle control.
A Complex Frequency Method for A Loaded Resonant Cavity of Transmission Lines
Institute of Scientific and Technical Information of China (English)
LIANGChanghong; LILong; SUTao; FANShengcai
2004-01-01
A complex frequency method for analyzing a loaded resonant cavity of transmission lines is presented in this paper. A sub-resonance system theory is used to treat the various loaded transmission lines cavity more effectively. Some practice examples are given to illustrate the application and validity of the proposed approach in this paper.
Influence of reed motion on the resonance frequency of reed-blown wood-wind instruments
Nederveen, C.J.
1969-01-01
When vibrating, the needs of wood wind instruments displace an amount of air that shifts the resonance frequency of the instrument in the same way as does a mouthpiece cavity. In cylindrical instruments, this shift corresponds to an effective lengthening of the resonating tube. In conical instrument
Magnetically tunable resonance frequency beam utilizing a stress-sensitive film
Energy Technology Data Exchange (ETDEWEB)
Davis, J. Kenneth (Kingston, TN); Thundat, Thomas G. (Knoxville, TN); Wachter, Eric A. (Oak Ridge, TN)
2001-01-01
Methods and apparatus for detecting particular frequencies of vibration utilize a magnetically-tunable beam element having a stress-sensitive coating and means for providing magnetic force to controllably deflect the beam element thereby changing its stiffness and its resonance frequency. It is then determined from the response of the magnetically-tunable beam element to the vibration to which the beam is exposed whether or not a particular frequency or frequencies of vibration are detected.
Electrostatically tunable resonance frequency beam utilizing a stress-sensitive film
Thundat, Thomas G.; Wachter, Eric A.; Davis, J. Kenneth
2001-01-01
Methods and apparatus for detecting particular frequencies of acoustic vibration utilize an electrostatically-tunable beam element having a stress-sensitive coating and means for providing electrostatic force to controllably deflect the beam element thereby changing its stiffness and its resonance frequency. It is then determined from the response of the electrostatically-tunable beam element to the acoustical vibration to which the beam is exposed whether or not a particular frequency or frequencies of acoustic vibration are detected.
Influence of random roughness on cantilever resonance frequency
Ergincan, O.; Palasantzas, G.
2010-01-01
In this paper we investigate the influence of random roughness on the oscillation frequency of cantilevers coated with thin film overlayers. First the theory expressions for the roughness-induced frequency shift are derived using the cantilever equation of motion. Subsequently it is shown that the r
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.
Nonlinear series resonance and standing waves in dual-frequency capacitive discharges
Wen, De-Qi; Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.; Wang, You-Nian
2017-01-01
It is well-known that the nonlinear series resonance in a high frequency capacitive discharge enhances the electron power deposition and also creates standing waves which produce radially center-high rf voltage profiles. In this work, the dynamics of series resonance and wave effects are examined in a dual-frequency driven discharge, using an asymmetric radial transmission line model incorporating a Child law sheath. We consider a cylindrical argon discharge with a conducting electrode radius of 15 cm, gap length of 3 cm, with a base case having a 60 MHz high frequency voltage of 250 V and a 10 MHz low frequency voltage of 1000 V, with a high frequency phase shift {φ\\text{H}}=π between the two frequencies. For this phase shift there is only one sheath collapse, and the time-averaged spectral peaks of the normalized current density at the center are mainly centered on harmonic numbers 30 and 50 of the low frequency, corresponding to the first standing wave resonance frequency and the series resonance frequency, respectively. The effects of the waves on the series resonance dynamics near the discharge center give rise to significant enhancements in the electron power deposition, compared to that near the discharge edge. Adjusting the phase shift from π to 0, or decreasing the low frequency from 10 to 2 MHz, results in two or more sheath collapses, respectively, making the dynamics more complex. The sudden excitation of the perturbed series resonance current after the sheath collapse results in a current oscillation amplitude that is estimated from analytical and numerical calculations. Self-consistently determining the dc bias and including the conduction current is found to be important. The subsequent slow time variation of the high frequency oscillation is analyzed using an adiabatic theory.
Zhang, Yulong; Wang, Tianyang; Zhang, Ai; Peng, Zhuoteng; Luo, Dan; Chen, Rui; Wang, Fei
2016-12-01
In this paper, we present design and test of a broadband electrostatic energy harvester with a dual resonant structure, which consists of two cantilever-mass subsystems each with a mass attached at the free edge of a cantilever. Comparing to traditional devices with single resonant frequency, the proposed device with dual resonant structure can resonate at two frequencies. Furthermore, when one of the cantilever-masses is oscillating at resonance, the vibration amplitude is large enough to make it collide with the other mass, which provides strong mechanical coupling between the two subsystems. Therefore, this device can harvest a decent power output from vibration sources at a broad frequency range. During the measurement, continuous power output up to 6.2-9.8 μW can be achieved under external vibration amplitude of 9.3 m/s2 at a frequency range from 36.3 Hz to 48.3 Hz, which means the bandwidth of the device is about 30% of the central frequency. The broad bandwidth of the device provides a promising application for energy harvesting from the scenarios with random vibration sources. The experimental results indicate that with the dual resonant structure, the vibration-to-electricity energy conversion efficiency can be improved by 97% when an external random vibration with a low frequency filter is applied.
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.
Zhou, Peng; Lu, Siliang; Liu, Fang; Liu, Yongbin; Li, Guihua; Zhao, Jiwen
2017-03-01
Stochastic resonance (SR), which is characterized by the fact that proper noise can be utilized to enhance weak periodic signals, has been widely applied in weak signal detection. SR is a nonlinear parameterized filter, and the output signal relies on the system parameters for the deterministic input signal. The most commonly used index for parameter tuning in the SR procedure is the signal-to-noise ratio (SNR). However, using the SNR index to evaluate the denoising effect of SR quantitatively is insufficient when the target signal frequency cannot be estimated accurately. To address this issue, six different indexes, namely, power spectral kurtosis of the SR output signal, correlation coefficient between the SR output and the original signal, peak SNR, structural similarity, root mean square error, and smoothness, are constructed in this study to measure the SR output quantitatively. These six quantitative indexes are fused into a new synthetic quantitative index (SQI) via a back propagation neural network to guide the adaptive parameter selection of the SR procedure. The index fusion procedure reduces the instability of each index and thus improves the robustness of parameter tuning. In addition, genetic algorithm is utilized to quickly select the optimal SR parameters. The efficiency of bearing fault diagnosis is thus further improved. The effectiveness and efficiency of the proposed SQI-based adaptive SR method for bearing fault diagnosis are verified through numerical and experiment analyses.
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.
Fourier Transform Ion Cyclotron Resonance Mass Spectrometry at the Cyclotron Frequency
Nagornov, Konstantin O.; Kozhinov, Anton N.; Tsybin, Yury O.
2017-02-01
The phenomenon of ion cyclotron resonance allows for determining mass-to-charge ratio, m/z, of an ensemble of ions by means of measurements of their cyclotron frequency, ω c . In Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), the ω c quantity is usually unavailable for direct measurements: the resonant state is located close to the reduced cyclotron frequency (ω+), whereas the ω c and the corresponding m/z values may be calculated via theoretical derivation from an experimental estimate of the ω+ quantity. Here, we describe an experimental observation of a new resonant state, which is located close to the ω c frequency and is established because of azimuthally-dependent trapping electric fields of the recently developed ICR cells with narrow aperture detection electrodes. We show that in mass spectra, peaks close to ω+ frequencies can be reduced to negligible levels relative to peaks close to ω c frequencies. Due to reduced errors with which the ω c quantity is obtained, the new resonance provides a means of cyclotron frequency measurements with precision greater than that achieved when ω+ frequency peaks are employed. The described phenomenon may be considered for a development into an FT-ICR MS technology with increased mass accuracy for applications in basic research, life, and environmental sciences.
Fourier Transform Ion Cyclotron Resonance Mass Spectrometry at the Cyclotron Frequency.
Nagornov, Konstantin O; Kozhinov, Anton N; Tsybin, Yury O
2017-04-01
The phenomenon of ion cyclotron resonance allows for determining mass-to-charge ratio, m/z, of an ensemble of ions by means of measurements of their cyclotron frequency, ω c . In Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), the ω c quantity is usually unavailable for direct measurements: the resonant state is located close to the reduced cyclotron frequency (ω+), whereas the ω c and the corresponding m/z values may be calculated via theoretical derivation from an experimental estimate of the ω+ quantity. Here, we describe an experimental observation of a new resonant state, which is located close to the ω c frequency and is established because of azimuthally-dependent trapping electric fields of the recently developed ICR cells with narrow aperture detection electrodes. We show that in mass spectra, peaks close to ω+ frequencies can be reduced to negligible levels relative to peaks close to ω c frequencies. Due to reduced errors with which the ω c quantity is obtained, the new resonance provides a means of cyclotron frequency measurements with precision greater than that achieved when ω+ frequency peaks are employed. The described phenomenon may be considered for a development into an FT-ICR MS technology with increased mass accuracy for applications in basic research, life, and environmental sciences. Graphical Abstract ᅟ.
Low Frequency Nuclear Quadrupole Resonance with SQUID Amplifiers
Clarke, John
1994-02-01
The dc SQUID (Superconducting QUantum Interference Device) can be configured as an amplifier of spin-echos with a noise temperature of approximately 10 mK (f/1 M Hz) at an operating temperature of 1.5 K. A Fourier transform spectrometer based on a SQUID with a superconducting input circuit and operated in a flux-locked loop is used to obtain nuclear quadrupole resonance (NQR) spectra in a broadband m ode over the bandwith 0 -1 M Hz. Spin-echo spectra of 14N in NH4ClO4 reveal sharp NQR resonances, obtained simultaneously, at 17.4, 38.8 and 56.2 kHz. At 1.5 K, the measured longitudinal and transverse relaxation times T1 and T2 for the 38.8 kHz transition are 63 ± 3 ms and 22±2 ms, respectively.
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.
Directory of Open Access Journals (Sweden)
Hong Men
2011-09-01
Full Text Available This study makes the three acryl glycerin polymers, oxidation three acryl glycerins, and low carbon number fatty acid as inferior oil feature index. Using double steady state stochastic resonance signal-to-noise ratio analysis methods make the quantitative analysis to inferior oil. This paper analyzes the stochastic resonance. Introduces the principle detection system structure based on adaptive multilayer stochastic resonance algorithm in inferior oil quantitativeanalysis; and make adaptive double stochastic resonance model and inferior oil as example, give the simulation and numerical analysis of this model of the system. The results show that the system can obtain more accurate quality the proportion of the inferior oil information. At the same time, this method can effectively solve the semiconductor gas sensors of the baseline drift problem. The method of stochastic resonance has a lot of application prospect in improving the system performance.
Creating Feshbach resonances for ultracold molecule formation with radio-frequency fields
Owens, Daniel J.; Xie, Ting; Hutson, Jeremy M.
2016-08-01
We show that radio-frequency (rf) radiation may be used to create Feshbach resonances in ultracold gases of alkali-metal atoms at desired magnetic fields that are convenient for atomic cooling and degeneracy. For the case of 39K+133Cs , where there are no rf-free resonances in regions where Cs may be cooled to degeneracy, we show that a resonance may be created near 21 G with 69.2 MHz rf radiation. This resonance is almost lossless with circularly polarized rf, and the molecules created are long-lived even with plane-polarized rf.
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...... the refractice index of the crystal and alters the optical path length of the cavity. This effect may lend to self-frequency locking of the OPO to a specific resonance of the signal and idler fields, and it also results in peculiarities in the transient response of the system as it is scanned through resonance...
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.
Xereas, George; Chodavarapu, Vamsy P.
2016-07-01
We present the design and development of breath-mode silicon ring resonators fabricated using a commercial pure-play microfabrication process that provides ultraclean wafer-level vacuum-encapsulation. The micromechanical resonators are fabricated in MEMS integrated design for inertial sensors process that is developed by Teledyne DALSA Semiconductor Inc. The ring resonators are designed to operate with a relatively low DC polarization voltage, starting at 5 V, while providing a high frequency-quality factor product. We study the quality of the vacuum packaging using an automated testing setup over an extended time period. We study the effect of motional resistance on the performance of MEMS resonators. The fabricated devices had a resonant frequency of 10 MHz with the quality factor exceeding 8.4×104.
Mapping nanoscale elasticity and dissipation using dual frequency contact resonance AFM
Energy Technology Data Exchange (ETDEWEB)
Gannepalli, A; Proksch, R [Asylum Research, Santa Barbara, CA (United States); Yablon, D G; Tsou, A H, E-mail: ganil@asylumresearch.com [Corporate Strategic Research, ExxonMobil Research and Engineering, Annandale, NJ (United States)
2011-09-02
We report on a technique that simultaneously quantifies the contact stiffness and dissipation of an AFM cantilever in contact with a surface, which can ultimately be used for quantitative nanomechanical characterization of surfaces. The method is based on measuring the contact resonance frequency using dual AC resonance tracking (DART), where the amplitude and phase of the cantilever response are monitored at two frequencies on either side of the contact resonance. By modelling the tip-sample contact as a driven damped harmonic oscillator, the four measured quantities (two amplitudes and two phases) allow the four model parameters, namely, drive amplitude, drive phase, resonance frequency and quality factor, to be calculated. These mechanical parameters can in turn be used to make quantitative statements about localized sample properties. We apply the method to study the electromechanical coupling coefficients in ferroelectric materials and the storage and loss moduli in viscoelastic materials.
Bertke, Maik; Hamdana, Gerry; Wu, Wenze; Marks, Markus; Suryo Wasisto, Hutomo; Peiner, Erwin
2016-10-01
The asymmetric resonance frequency analysis of silicon cantilevers for a low-cost wearable airborne nanoparticle detector (Cantor) is described in this paper. The cantilevers, which are operated in the fundamental in-plane resonance mode, are used as a mass-sensitive microbalance. They are manufactured out of bulk silicon, containing a full piezoresistive Wheatstone bridge and an integrated thermal heater for reading the measurement output signal and stimulating the in-plane excitation, respectively. To optimize the sensor performance, cantilevers with different cantilever geometries are designed, fabricated and characterized. Besides the resonance frequency, the quality factor (Q) of the resonance curve has a high influence concerning the sensor sensitivity. Because of an asymmetric resonance behaviour, a novel fitting function and method to extract the Q is created, different from that of the simple harmonic oscillator (SHO). For testing the sensor in a long-term frequency analysis, a phase- locked loop (PLL) circuit is employed, yielding a frequency stability of up to 0.753 Hz at an Allan variance of 3.77 × 10-6. This proposed asymmetric resonance frequency analysis method is expected to be further used in the process development of the next-generation Cantor.
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.
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 h...
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.
A robust adaptive load frequency control for micro-grids.
Khooban, Mohammad-Hassan; Niknam, Taher; Blaabjerg, Frede; Davari, Pooya; Dragicevic, Tomislav
2016-11-01
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 micro-grid (MG) is introduced that can consider electric vehicles׳ (EV(s)) effect. Moreover, in this paper, a new combination of the General Type II Fuzzy Logic Sets (GT2FLS) and the Modified Harmony Search Algorithm (MHSA) technique is applied for adaptive tuning of proportional-integral (PI) 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 wind farm in Sweden and solar radiation data in Aberdeen (United Kingdom) was used in order to examine the performance of the proposed novel controller. A comparison is made between the achieved results of Optimal Fuzzy-PI (OFPI) controller and those of Optimal Interval Type II Fuzzy-PI (IT2FPI) controller, which are of most recent advances in the area at hand. The Simulation results prove the successfulness and effectiveness of the proposed controller.
Gao, Zhen; Gao, Fei; Shastri, Kunal Krishnaraj; Zhang, Baile
2016-01-01
Localized spoof surface plasmon polaritons (spoof-SPPs) in a graded spoof-plasmonic resonator chain with linearly increasing spacing are experimentally investigated at microwave frequencies. Transmission measurements and direct near-field mappings on this graded chain show that the propagation of localized spoof-SPPs can be cutoff at different positions along the graded chain under different frequencies due to the graded coupling between adjacent resonators. This mechanism can be used to guide localized spoof-SPPs in the graded chain to specific positions depending on the frequency and thereby implement a device that can work as a selective switch in integrated plasmonic circuits. PMID:27149656
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.
Bi-Frequency Modulated Quasi-Resonant Converters: Theory and Applications
Zhang, Yuefeng
1995-01-01
To avoid the variable frequency operation of quasi -resonant converters, many soft-switching PWM converters have been proposed, all of them require an auxiliary switch, which will increase the cost and complexity of the power supply system. In this thesis, a new kind of technique for quasi -resonant converters has been proposed, which is called the bi-frequency modulation technique. By operating the quasi-resonant converters at two switching frequencies, this technique enables quasi-resonant converters to achieve the soft-switching, at fixed switching frequencies, without an auxiliary switch. The steady-state analysis of four commonly used quasi-resonant converters, namely, ZVS buck, ZCS buck, ZVS boost, and ZCS boost converter has been presented. Using the concepts of equivalent sources, equivalent sinks, and resonant tank, the large signal models of these four quasi -resonant converters were developed. Based on these models, the steady-state control characteristics of BFM ZVS buck, BFM ZCS buck, BFM ZVS boost, and BFM ZCS boost converter have been derived. The functional block and design consideration of the bi-frequency controller were presented, and one of the implementations of the bi-frequency controller was given. A complete design example has been presented. Both computer simulations and experimental results have verified that the bi-frequency modulated quasi-resonant converters can achieve soft-switching, at fixed switching frequencies, without an auxiliary switch. One of the application of bi-frequency modulation technique is for EMI reduction. The basic principle of using BFM technique for EMI reduction was introduced. Based on the spectral analysis, the EMI performances of the PWM, variable-frequency, and bi-frequency modulated control signals was evaluated, and the BFM control signals show the lowest EMI emission. The bi-frequency modulated technique has also been applied to the power factor correction. A BFM zero -current switching boost converter has
A novel approach for the fine tuning of resonance frequency of patch antenna
Mathur, Monika; Singh, Ghanshyam; Bhatnagar, S. K.
2013-01-01
When a patch antenna is fabricated, dimensions of the patch may be slightly different from the designed values due to tolerances in the fabrication process. This alters the resonance frequency of the antenna. To overcome this problem this paper presents a new design approach for fine tuning the resonance frequency by dielectric constant engineering. This approach is especially suited to low temperature co-fired ceramic (LTCC) and similar processes where the antenna dielectric is composed of several layers. Composite dielectric constant of this multilayer structure is altered in such a way that the resonant frequency is set back to the designed value. It has been verified that for proposed micro strip antenna (MSA) design, the frequency-area curve follows a quadratic relation with a variable R (Ratio of cavity area to the patch area). This mathematical model is true up to R 1.27. After this saturation effects set in and the curve follows a straight line behavior.≡
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.
Frequency Adaptive Repetitive Control of Grid-Tied Single-Phase PV Inverters
DEFF Research Database (Denmark)
Zhou, Keliang; Yang, Yongheng; Blaabjerg, Frede
2015-01-01
. This paper thus explores a frequency adaptive repetitive control strategy for grid converters, which employs fractional delay filters in order to adapt to the change of the grid frequency. Case studies with experimental results of a single-phase grid-connected PV inverter system are provided to verify...
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.
A frequency up-converting harvester based on internal resonance in 2-DOF nonlinear systems
Wu, Yipeng; Qiu, Jinhao; Ji, Hongli
2016-11-01
This paper reports the design and experimental testing of a novel frequency up- converting piezoelectric energy harvester. The harvester is firstly approximated as a 2-degree- of-freedom cubic nonlinear system instead of the general Duffing systems. A 1:3 internal resonance innovatively applied in the frequency up-conversion approach is thoroughly investigated. Finally, the theoretical dynamic model confirmed by the experimental results clearly shows the effect of the frequency up-conversion.
Diode-laser frequency stabilization based on the resonant Faraday effect
Wanninger, P.; Valdez, E. C.; Shay, T. M.
1992-01-01
The authors present the results of a method for frequency stabilizing laser diodes based on the resonant Faraday effects. A Faraday cell in conjunction with a polarizer crossed with respect to the polarization of the laser diode comprises the intracavity frequency selective element. In this arrangement, a laser pull-in range of 9 A was measured, and the laser operated at a single frequency with a linewidth less than 6 MHz.
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).
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
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......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...
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
This paper proposes an adaptive rotor current controller for doubly-fed induction generator (DFIG), which consists of a proportional (P) controller and two harmonic resonant (R) controllers implemented in the rotor rotating reference frame. The two resonant controllers are tuned at slip frequencies ωslip+ and ωslip-, respectively. As a result, the positive- and negative-sequence components of the rotor current are fully regulated by the PR controller without involving the positive- and negative-sequence decomposition, which in effect improves the fault ride-through (FRT) capability of the DFIG-based wind power generation system during the period of large transient grid voltage unbalance. Correctness of the theoretical analysis and feasibility of the proposed unbalanced control scheme are validated by simulation on a 1.5-MW DFIG wind power generation system.
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....
Neural Network Model Of The PXIE RFQ Cooling System and Resonant Frequency Response
Energy Technology Data Exchange (ETDEWEB)
Edelen, Auralee [Fermilab; Biedron, Sandra [Colorado State U., Fort Collins; Bowring, Daniel [Fermilab; Chase, Brian [Fermilab; Edelen, Jonathan [Fermilab; Milton, Stephen [Colorado State U., Fort Collins; Steimel, Jim [Fermilab
2016-06-01
As part of the PIP-II Injector Experiment (PXIE) accel-erator, a four-vane radio frequency quadrupole (RFQ) accelerates a 30-keV, 1-mA to 10-mA H' ion beam to 2.1 MeV. It is designed to operate at a frequency of 162.5 MHz with arbitrary duty factor, including continuous wave (CW) mode. The resonant frequency is controlled solely by a water-cooling system. We present an initial neural network model of the RFQ frequency response to changes in the cooling system and RF power conditions during pulsed operation. A neural network model will be used in a model predictive control scheme to regulate the resonant frequency of the RFQ.
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.
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.
Impedance-Based High Frequency Resonance Analysis of DFIG System in Weak Grids
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
The impedance-based model of Doubly Fed Induction Generator (DFIG) systems, including the rotor part (Rotor Side Converter (RSC) and induction machine), and the grid part (Grid Side Converter (GSC) and its output filter), has been developed for analysis and mitigation of the Sub- Synchronous Resonance (SSR). However, the High Frequency Resonance (HFR) of DFIG systems due to the impedance interaction between DFIG system and parallel compensated weak network is often overlooked. This paper thus...
Frequency map analysis of resonances in a nonlinear lattice with space charge
Energy Technology Data Exchange (ETDEWEB)
Turchetti, G. E-mail: turchetti@bo.infn.it; Bazzani, A.; Bergamini, F.; Rambaldi, S.; Hofmann, I.; Bongini, L.; Franchetti, G
2001-05-21
In storage rings for heavy ion fusion beam losses must be minimized. During bunch compression high space charge is reached and the reciprocal effects between the collective modes of the beam and the single particle lattice nonlinearities must be considered to understand the problem of resonance crossing and halo formation. We show that the frequency map analysis of particle in core models gives an adequate description of the resonance network and of the chaotic regions where the halo particles can diffuse.
Resonant magneto-optic rotation for magnetometry using autonomous frequency stabilization
Pradhan, S; Behera, R; Poornima,; Dasgupta, K
2014-01-01
The operation of a high sensitive atomic magnetometer using resonant elliptically polarized light is demonstrated. The experimental geometry allows autonomous frequency stabilization of the laser, thereby offers compact operation of the overall device. The magnetometry is based on measurement of the zero magnetic field resonance in degenerate two level system using polarimetric detection and has a preliminary sensitivity of <10 pT/Hz1/2 @ 1 Hz.
High Frequency Resonance Damping of DFIG based Wind Power System under Weak Network
DEFF Research Database (Denmark)
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
When operating in a micro or weak grid which has a relatively large network impedance, the Doubly Fed Induction Generator (DFIG) based wind power generation system is prone to suffer high frequency resonance due to the impedance interaction between DFIG system and the parallel compensated network...... (series RL + shunt C). In order to improve the performance of the DFIG system as well as other units and loads connected to the weak grid, the high frequency resonance needs to be effectively damped. In this paper, the proposed active damping control strategy is able to implement effective damping either...... 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...
Low frequency wireless power transfer using modified parallel resonance matching at a complex load
Directory of Open Access Journals (Sweden)
Artit Rittiplang
2016-10-01
Full Text Available In the Impedance Matching (IM condition of Wireless Power Transfer (WPT, series resonant and strong coupling structures have been widely studied which operate at an optimal parameter, a resistive load, and the high resonant frequency of greater than 1 MHz. However, i The optimal parameter (particular value limits the design, ii the common loads are complex, iii The high frequency RF sources are usually inefficient. This paper presents a modified parallel resonant structure that can operate at a low frequency of 15 kHz without an optimal parameter under the IM condition with a complex load, and the calculated efficiency is equal to 71.2 % at 5-cm transfer distance.
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.
Chindam, Chandraprakash; Nama, Nitesh; Ian Lapsley, Michael; Costanzo, Francesco; Jun Huang, Tony
2013-11-21
Bubble-based microfluidic devices have been proven to be useful for many biological and chemical studies. These bubble-based microdevices are particularly useful when operated at the trapped bubbles' resonance frequencies. In this work, we present an analytical expression that can be used to predict the resonant frequency of a bubble trapped over an arbitrary shape. Also, the effect of viscosity on the dispersion characteristics of trapped bubbles is determined. A good agreement between experimental data and theoretical results is observed for resonant frequency of bubbles trapped over different-sized rectangular-shaped structures, indicating that our expression can be valuable in determining optimized operational parameters for many bubble-based microfluidic devices. Furthermore, we provide a close estimate for the harmonics and a method to determine the dispersion characteristics of a bubble trapped over circular shapes. Finally, we present a new method to predict fluid properties in microfluidic devices and complement the explanation of acoustic microstreaming.
DEFF Research Database (Denmark)
Tang, Yi; Yao, Wenli; Loh, Poh Chiang
2016-01-01
, and this observation is so far not discussed in the literature. In this case, a very cost-effective LCL filter design can be achieved for the grid-connected converters, whose dominant switching harmonics may appear at double the switching frequency, e.g., in unipolar-modulated three-level full-bridge converters and 12......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......-switch-based three-phase pulsewidth-modulated converters. Moreover, a single-loop current control strategy is proposed for the designed LCL filter, and the control system is inherently stable without introducing any passive or active damping. Based on the new stability region, two LCL filter design...
DEFF Research Database (Denmark)
Tang, Yi; Yao, Wenli; Loh, Poh Chiang
2015-01-01
, and this observation is so far not discussed in the literature. In this case, very cost-effective LCL-filter design can be achieved for grid-connected converters whose dominant switching harmonics may appear at double of the switching frequency, e.g. in unipolar modulated three-level full bridge converters and 12......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......-switch based three-phase pulse-width modulated (PWM) converters. Moreover, a single-loop current control strategy is proposed for the designed LCL-filter, and the control system is inherently stable without introducing any passive or active damping. Experimental results, showing the high quality output...
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.
Piezoelectrically tunable resonance frequency beam utilizing a stress-sensitive film
Energy Technology Data Exchange (ETDEWEB)
Thundat, Thomas G. (Knoxville, TN); Wachter, Eric A. (Oak Ridge, TN)
2002-01-01
Methods and apparatus for detecting particular frequencies of acoustic vibration utilize a piezoelectrically-tunable beam element having a piezoelectric layer and a stress sensitive layer and means for providing an electrical potential across the piezoelectric layer to controllably change the beam's stiffness and thereby change its resonance frequency. It is then determined from the response of the piezoelectrically-tunable beam element to the acoustical vibration to which the beam element is exposed whether or not a particular frequency or frequencies of acoustic vibration are detected.
Piezoelectrically tunable resonance frequency beam utilizing a stress-sensitive film
Thundat, Thomas G.; Wachter, Eric A.
2002-01-01
Methods and apparatus for detecting particular frequencies of acoustic vibration utilize a piezoelectrically-tunable beam element having a piezoelectric layer and a stress sensitive layer and means for providing an electrical potential across the piezoelectric layer to controllably change the beam's stiffness and thereby change its resonance frequency. It is then determined from the response of the piezoelectrically-tunable beam element to the acoustical vibration to which the beam element is exposed whether or not a particular frequency or frequencies of acoustic vibration are detected.
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.
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...
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.
Fu, J C; Chen, C C; Chai, J W; Wong, S T C; Li, I C
2010-06-01
We propose an automatic hybrid image segmentation model that integrates the statistical expectation maximization (EM) model and the spatial pulse coupled neural network (PCNN) for brain magnetic resonance imaging (MRI) segmentation. In addition, an adaptive mechanism is developed to fine tune the PCNN parameters. The EM model serves two functions: evaluation of the PCNN image segmentation and adaptive adjustment of the PCNN parameters for optimal segmentation. To evaluate the performance of the adaptive EM-PCNN, we use it to segment MR brain image into gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF). The performance of the adaptive EM-PCNN is compared with that of the non-adaptive EM-PCNN, EM, and Bias Corrected Fuzzy C-Means (BCFCM) algorithms. The result is four sets of boundaries for the GM and the brain parenchyma (GM+WM), the two regions of most interest in medical research and clinical applications. Each set of boundaries is compared with the golden standard to evaluate the segmentation performance. The adaptive EM-PCNN significantly outperforms the non-adaptive EM-PCNN, EM, and BCFCM algorithms in gray mater segmentation. In brain parenchyma segmentation, the adaptive EM-PCNN significantly outperforms the BCFCM only. However, the adaptive EM-PCNN is better than the non-adaptive EM-PCNN and EM on average. We conclude that of the three approaches, the adaptive EM-PCNN yields the best results for gray matter and brain parenchyma segmentation.
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...
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.
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.
Li, Xian-Fang; Tang, Guo-Jin; Shen, Zhi-Bin; Lee, Kang Yong
2015-01-01
Free vibration and mass detection of carbon nanotube-based sensors are studied in this paper. Since the mechanical properties of carbon nanotubes possess a size effect, the nonlocal beam model is used to characterize flexural vibration of nanosensors carrying a concentrated nanoparticle, where the size effect is reflected by a nonlocal parameter. For nanocantilever or bridged sensor, frequency equations are derived when a nanoparticle is carried at the free end or the middle, respectively. Exact resonance frequencies are numerically determined for clamped-free, simply-supported, and clamped-clamped resonators. Alternative approximations of fundamental frequency are given in closed form within the relative error less than 0.4%, 0.6%, and 1.4% for cantilever, simply-supported, and bridged sensors, respectively. Mass identification formulae are derived in terms of the frequency shift. Identified masses via the present approach coincide with those using the molecular mechanics approach and reach as low as 10(-24)kg. The obtained results indicate that the nonlocal effect decreases the resonance frequency except for the fundamental frequency of nanocantilever sensor. These results are helpful to the design of micro/nanomechanical zeptogram-scale biosensor.
Dual-frequency ferromagnetic resonance to measure spin current coupling in multilayers
Adur, Rohan; Du, Chunhui; Wang, Hailong; Manuilov, Sergei A.; Yang, Fengyuan; Hammel, P. Chris
2014-08-01
Spin pumping is a method for injecting a pure spin current into a non-magnetic metal (NM) by inducing precession of a neighboring ferromagnet (FM) at its ferromagnetic resonance frequency. A popular method to detect spin current uses the Inverse Spin Hall Effect (ISHE) to convert the spin current to a detectable charge current and hence a voltage. In order to better understand the role of time independent and high frequency contributions to spin pumping, we sought to detect we attempt to detect spin currents by using a second microwave frequency to detect changes in linewidth of a second ferromagnet due to the spin-torque induced by the spin current from the first ferromagnet. This dual resonance is achieved by pairing a custom broadband coplanar transmission line with the high-Q resonant cavity of a commercial electron paramagnetic resonance spectrometer. This technique is general enough that it should enable the investigation of spin currents in any FM-NM-FM system, for any orientation of external field, and is not sensitive to voltage artifacts often found in ISHE measurements. We find that the condition for simultaneous resonance generates a dc spin current that is too small to produce a measurable change in linewidth of the second ferromagnet, confirming the dominance of ac spin currents in linewidth enhancement measurements.
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.
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...
Effects of Dielectric Substrates and Ground Planes on Resonance Frequency of Archimedean Spirals.
Hooker, Jerris W; Ramaswamy, Vijaykumar; Arora, Rajendra K; Edison, Arthur S; Brey, William W
2016-04-01
Superconducting self-resonant spiral structures are of current interest for applications both in metamaterials and as probe coils for nuclear magnetic resonance (NMR) spectroscopy for high-sensitivity chemical analysis. Accurate spiral models are available in the literature for behavior of a spiral below and up to self-resonance. However, knowledge of the higher modes is also important. We present the relationships between the spiral parameters and the multiple mode frequencies of single sided spirals on dielectric substrates as modeled by method of moments simulation. In the absence of a ground plane, we find that the mode frequency has a linear though not necessarily harmonic dependence on the mode number. The effect of a thick substrate can be approximated by an effective dielectric constant. But when the thickness is less than 20% of the spiral trace width (router - rinner) this approximation is no longer accurate. We have developed a simple empirical formula to predict the higher modes.
Ultra-thin wideband magnetic-type metamaterial absorber based on LC resonator at low frequencies
Zhang, Linbo; Zhou, Peiheng; Chen, Haiyan; Lu, Haipeng; Xie, Jianliang; Deng, Longjiang
2015-10-01
In this paper, we propose to realize a broad absorption band in the frequency regimes of 2-6 GHz based on multiple resonances. A magnetic-type metamaterial absorber with cross-arrow pattern is further demonstrated numerically and experimentally. Two absorption resonances are generated by LC resonance, leading to bandwidth expansion. The equivalent circuit theory and the surface current distributions of the proposed absorber are discussed to analyze the physical mechanism. Moreover, the broad bandwidth can be maintained as incident angle up to 30° for transverse electric polarization and 45° for transverse magnetic polarization. Finally, experimental results show that the proposed absorber with the total thickness of 2.4 mm exhibits a -10 dB absorption bandwidth by more than 70 %. The low-frequency absorber has potential applications in the area of eliminating microwave energy.
Gagliardi, G; De Nicola, S; Ferraro, P; De Natale, P
2007-04-02
We report on an optically-based technique that provides an efficient way to track static and dynamic strain by locking the frequency of a diode laser to a fiber Bragg-grating Fabry-Pérot cavity. For this purpose, a suitable optical frequency discriminator is generated exploiting the fiber natural birefringence and that resulting from the gratings inscription process. In our scheme, a polarization analyzer detects dispersive-shaped signals centered on the cavity resonances without need for additional optical elements in the resonator or any laser-modulation technique. This method prevents degradation of the resonator quality and maintains the configuration relatively simple, demonstrating static and dynamic mechanical sensing below the picostrain level.
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...... be proportionally improved by increasing the length of the optical fiber ring resonator....... 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...
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...
Computation of high frequency fields in resonant cavities based on perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Brackebusch, Korinna; Glock, Hans-Walter; Rienen, Ursula van [Universitaet Rostock (Germany). Institut fuer Allgemeine Elektrotechnik
2012-07-01
The eigenmodes of an accelerator cavity are essential for the determination of its performance characteristics, comprising resonant frequencies and field distributions inside the cavity. Apart from the material properties the eigenmodes depend on the cavity geometry. Due to manufacturing tolerances and operational demands deviations of the actual cavity shape from the desired one are inevitable. Any geometry perturbation results in a shift of the resonant frequencies and modified field distributions. Slater's theorem offers an efficient way to compute the changed resonant frequencies, however, not the changed fields. In this work, we will analyse a generalisation of Slater's theorem proposed in literature. The method enables the computation of the resonant frequencies and the field distributions of a slightly perturbed cavity by using a set of eigenmodes of the unperturbed cavity. We evaluate the practicability of the method by applying it to cavity geometries for which the eigenmodes are analytically known, ascertain the effort of reasonable computation results and describe the limitations of the method.
2000-09-29
electromagnetic waves by a Narrow anisotropically conductive strip," Radiotekh. Elektron ., vol. 44, no. 7, pp. 800-805, 1999. [3] A. N. Sivov, A. D...Chuprin, and A. D. Shatrov, "Low-frequency resonance in a hollow circular cylinder with perfect conductivity along helical lines," Radiotekh. Elektron
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…
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 ea...
Measurement of the Resonant Frequency of Nano-Scale Cantilevers by Hard Contact Readout
DEFF Research Database (Denmark)
Dohn, Søren; Hansen, Ole; Bolsen, A.
2008-01-01
It is shown that detection of the resonant frequency of a nano-scale cantilever is possible by measuring the time average current flowing from an electrode to the cantilever during hard contact occurring twice every cycle of the cantilever vibration. The electronic detection method is insensitive....... The readout method is thereby ideally suited for portable sensor systems....
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.
Maimone, F; Tinschert, K; Celona, L; Lang, R; Mäder, J; Rossbach, J; Spädtke, P
2012-02-01
The properties of the electromagnetic waves heating the electrons of the ECR ion sources (ECRIS) plasma affect the features of the extracted ion beams such as the emittance, the shape, and the current, in particular for higher charge states. The electron heating methods such as the frequency tuning effect and the double frequency heating are widely used for enhancing the performances of ECRIS or even for the routine operation during the beam production. In order to better investigate these effects the CAPRICE ECRIS has been operated using these techniques. The ion beam properties for highly charged ions have been measured with beam diagnostic tools. The reason of the observed variations of this performance can be related to the different electromagnetic field patterns, which are changing inside the plasma chamber when the frequency is varying.
SOGI-FLL Based Adaptive Filter for DSTATCOM Under Variable Supply Frequency
Puranik, Vishal; Arya, Sabha Raj
2016-12-01
This paper presents an adaptive filter based on second order generalized integrator-frequency locked loop (SOGI-FLL) for distribution static compensator (DSTATCOM) operating under variable supply frequency with nonlinear load. It is observed that under variable supply frequency, the FLL provides an excellent frequency tracking performance. Necessary compensation can be provided by DSTATCOM at any frequency with the help of SOGI-FLL. The MATLAB simulink model of DSTATCOM is developed with SOGI-FLL based control algorithm and rectifier based nonlinear load. This three wire system is simulated in power factor correction and zero voltage regulation mode under variable supply frequency.
FREQUENCY SHIFTS OF RESONANT MODES OF THE SUN DUE TO NEAR-SURFACE CONVECTIVE SCATTERING
Energy Technology Data Exchange (ETDEWEB)
Bhattacharya, J.; Hanasoge, S.; Antia, H. M. [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai-400005 (India)
2015-06-20
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. We show that the full oscillation equations, in the presence of temporally stationary three-dimensional (3D) flows, can be reduced to an effective “quiet-Sun” wave equation with altered sound speed, Brünt–Väisäla frequency, and Lamb frequency. We derive the modified equation and relations for the appropriate averaging of 3D flows and thermal quantities to obtain the properties of this effective medium. Using flows obtained from 3D numerical simulations of near-surface convection, we quantify their effect on solar oscillation frequencies and find that they are shifted systematically and substantially. We argue therefore that consistent interpretations of resonant frequencies must include modifications to the wave equation that effectively capture the impact of vigorous hydrodynamic convection.
DEFF Research Database (Denmark)
Ghasemi, Negareh; Zare, Firuz; Davari, Pooya;
2017-01-01
Several factors can affect performance of an ultrasound system such as quality of excitation signal and ultrasound transducer behaviour. Nonlinearity of piezoelectric ultrasound transducers is a key determinant in designing a proper driving power supply. Although, the nonlinearity of piezoelectric...... transducer impedance has been discussed in different literatures, the trend of the nonlinearity at different frequencies with respect to excitation voltage variations has not been clearly investigated in practice. In this paper, to demonstrate how the nonlinearity behaves, a sandwich piezoceramic transducer...
Milián, Carles; Taki, Majid; Yulin, Alexey V; Skryabin, Dmitry V
2015-01-01
The influence of Raman scattering and higher order dispersions on solitons and frequency comb generation in silica microring resonators is investigated. The Raman effect introduces a threshold value in the resonator quality factor above which the frequency locked solitons can not exist and, instead, a rich dynamics characterized by generation of self-frequency shift- ing solitons and dispersive waves is observed. A mechanism of broadening of the Cherenkov radiation through Hopf instability of the frequency locked solitons is also reported.
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.
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.
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.
Orientation and Spatial Frequency Selectivity following Adaptation: A Reaction Time Study.
Plainis, Sotiris; Parry, Neil R A; Sapountzis, Panagiotis; Murray, Ian J
2015-03-01
The aim of the study was to determine orientation and spatial frequency sensitivity using reaction times (RTs) in an adaptation paradigm. Simple RTs were measured to the onset of a Gabor patch (SD = 1.2 deg, spatial frequency = 4 cycles deg(-1)). Observers adapted for 10 s to a 4 cycles deg(-1) grating presented at a series of orientations (0, 2, 5, 10, 22.5, 45, 90°) or spatial frequencies (±0.5, 1, and 2 octaves). The contrast of the test grating was 4x each participant's unadapted threshold. The effect of adaptation was evaluated by transforming RTs to effective contrast reduction using RT-based contrast response functions. RTs increased by between ∼ 100 ms to 150 ms when the test and adapting gratings were of the same orientation or spatial frequency. The effect became less pronounced as the difference in orientation or spatial frequency increased. The average bandwidths for orientation and spatial frequency were 17.4° and 1.24 octaves, respectively. The method has some advantages over traditional approaches. It reveals a rapid time course of adaptation recovery with a half-life of about 13 s to 23 s. RTs form a rapid and easily implemented technique for assessing the underlying physiological mechanisms that control adaptation at suprathreshold levels of contrast.
Potential of ion cyclotron resonance frequency current drive via fast waves in DEMO
Kazakov, Ye O.; Van Eester, D.; Wauters, T.; Lerche, E.; Ongena, J.
2015-02-01
For the continuous operation of future tokamak-reactors like DEMO, non-inductively driven toroidal plasma current is needed. Bootstrap current, due to the pressure gradient, and current driven by auxiliary heating systems are currently considered as the two main options. This paper addresses the current drive (CD) potential of the ion cyclotron resonance frequency (ICRF) heating system in DEMO-like plasmas. Fast wave CD scenarios are evaluated for both the standard midplane launch and an alternative case of exciting the waves from the top of the machine. Optimal ICRF frequencies and parallel wave numbers are identified to maximize the CD efficiency. Limitations of the high frequency ICRF CD operation are discussed. A simplified analytical method to estimate the fast wave CD efficiency is presented, complemented with the discussion of its dependencies on plasma parameters. The calculated CD efficiency for the ICRF system is shown to be similar to those for the negative neutral beam injection and electron cyclotron resonance heating.
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.
Institute of Scientific and Technical Information of China (English)
MAO Hai-yan; WANG Fu-ren; MENG Shu-chao; MAO Bo; LI Zhuang-zhi; NIE Rui-juan; LIU Xin-yuan; DAI Yuan-dong
2006-01-01
A new type of HTc superconducting film combshape resonator for radio frequency superconducting quantum interference devices (RF SQUID) has been designed.This new type of superconducting film comb-shape resonator is formed by a foursquare microstrip line without a flux concentrator.The range of the center frequency of this type of resonator varies from 800 MHz to 1300 MHz by changing the length of the teeth.In this paper,we report on simulating the relationship of the value of the center frequency and the length of the teeth,and testing the noise of HTc RF SQUID coupling this comb-shape resonator.
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.
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.
2014-09-17
AFRL-OSR-VA-TR-2014-0255 ADAPTIVE PIEZOELECTRIC CIRCUITRY SENSOR NETWORK KON-WELL WANG MICHIGAN UNIV ANN ARBOR Final Report 09/17/2014 DISTRIBUTION A...by ANSI Std. Z39.18 09-09-2014 Final Performance Report 06-01-2011 - 05-31-2014 Adaptive Piezoelectric Circuitry Sensor Network with High-Frequency...approach. Specifically, we propose to create a new concept of adaptive high-frequency piezoelectric self-sensing interrogation by means of tunable
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.
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.
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}.
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.
DEFF Research Database (Denmark)
Iwaszczuk, Krzysztof; Bisgaard, Christer Zoffmann; Andronico, Alessio;
2013-01-01
We investigate the electromagnetic design of whispering gallery mode (WGM) terahertz (THz) resonators. Terahertz radiation is generated by difference-frequency mixing of two electrically pumped high-order near-infrared laser WGM's at room temperature in the active cavity. Due to the leaky nature...... 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...
A novel radio frequency coil for veterinary magnetic resonance imaging system
Meng, Bin; Huang, Kai-Wen; Wang, Wei-Min
2010-07-01
In this article, a novel designed radio frequency (RF) coil is designed and built for the imaging of puppies in a V-shape permanent magnetic resonance imaging (MRI) system. Two sets of Helmholtz coil pairs with a V-shape structure are used to improve the holding of an animal in the coil. The homogeneity and the sensitivity of the RF field in the coil are analysed by theoretical calculation. The size and the shape of the new coil are optimized and validated by simulation through using the finite element method (FEM). Good magnetic resonance (MR) images are achieved on a shepherd dog.
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.
Multi frequency excited MEMS cantilever beam resonator for Mixer-Filter applications
Chandran, Akhil A.
2016-09-15
Wireless communication uses Radio Frequency waves to transfer information from one point to another. The modern RF front end devices are implementing MEMS in their designs so as to exploit the inherent properties of MEMS devices, such as its low mass, low power consumption, and small size. Among the components in the RF transceivers, band pass filters and mixers play a vital role in achieving the optimum RF performance. And this paper aims at utilizing an electrostatically actuated micro cantilever beam resonator\\'s nonlinear frequency mixing property to realize a Mixer-Filter configuration through multi-frequency excitation. The paper studies about the statics and dynamics of the device. Simulations are carried out to study the added benefits of multi frequency excitation. The modelling of the cantilever beam has been done using a Reduced Order Model of the Euler-Bernoulli\\'s beam equation by implementing the Galerkin discretization. The device is shown to be able to down-convert signals from 960 MHz of frequency to an intermediate frequency around 50 MHz and 70 MHz in Phase 1 and 2, respectively. The simulation showed promising results to take the project to the next level. © 2016 IEEE.
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.
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.
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.
On-line adaptive line frequency noise cancellation from a nuclear power measuring channel
Directory of Open Access Journals (Sweden)
Qadir Javed
2011-01-01
Full Text Available On-line software for adaptively canceling 50 Hz line frequency noise has been designed and tested at Pakistan Research Reactor 1. Line frequency noise causes much problem in weak signals acquisition. Sometimes this noise is so dominant that original signal is totally corrupted. Although notch filter can be used for eliminating this noise, but if signal of interest is in close vicinity of 50 Hz, then original signal is also attenuated and hence overall performance is degraded. Adaptive noise removal is a technique which could be employed for removing line frequency without degrading the desired signal. In this paper line frequency noise has been eliminated on-line from a nuclear power measuring channel. The adaptive LMS algorithm has been used to cancel 50 Hz noise. The algorithm has been implemented in labVIEW with NI 6024 data acquisition card. The quality of the acquired signal has been improved much as can be seen in experimental results.
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.
Impedance-Based High Frequency Resonance Analysis of DFIG System in Weak Grids
DEFF Research Database (Denmark)
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
The impedance-based model of Doubly Fed Induction Generator (DFIG) systems, including the rotor part (Rotor Side Converter (RSC) and induction machine), and the grid part (Grid Side Converter (GSC) and its output filter), has been developed for analysis and mitigation of the Sub- Synchronous...... Resonance (SSR). However, the High Frequency Resonance (HFR) of DFIG systems due to the impedance interaction between DFIG system and parallel compensated weak network is often overlooked. This paper thus investigates the impedance characteristics of DFIG systems for the analysis of HFR. The influences...... of the rotor speed variation, the machine mutual inductance and the digital control delay are evaluated. Two resonances phenomena are revealed, i.e., 1) the series HFR between the DFIG system and weak power grid; 2) the parallel HFR between the rotor part and the grid part of DFIG system. The impedance...
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.
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.
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.
Generation of high-frequency combs locked to atomic resonances by quantum phase modulation
Liu, Zuoye; Cavaletto, Stefano M; Harman, Zoltán; Keitel, Christoph H; Pfeifer, Thomas
2013-01-01
A general mechanism for the generation of frequency combs referenced to atomic resonances is put forward. The mechanism is based on the periodic phase control of a quantum system's dipole response. We develop an analytic description of the comb spectral structure, depending on both the atomic and the phase-control properties. We further suggest an experimental implementation of our scheme: Generating a frequency comb in the soft-x-ray spectral region, which can be realized with currently available techniques and radiation sources. The universality of this mechanism allows the generalization of frequency-comb technology to arbitrary frequencies, including the hard-x-ray regime by using reference transitions in highly charged ions.
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...
High frequency surface acoustic wave resonator-based sensor for particulate matter detection
Thomas, Sanju; Cole, Marina; Villa-López, Farah Helue; Gardner, J. W.
2016-01-01
This paper describes the characterization of high frequency Surface Acoustic Wave Resonator-based (SAWR) sensors, for the detection of micron and sub-micron sized particles. The sensor comprises two 262 MHz ST-cut quartz based Rayleigh wave SAWRs where one is used for particle detection and the other as a reference. Electro-acoustic detection of different sized particles shows a strong relationship between mass sensitivity (Δf/Δm) and particle diameter (Dp). This enables frequency-dependent S...
Directory of Open Access Journals (Sweden)
Shishir Shanker Punjala
2015-01-01
Full Text Available A novel broadband reconfigurable antenna design that can cover different frequency bands is presented. This antenna has multiple resonant frequencies. The reflection coefficient graphs for this antenna are presented in this paper. The new proposed design was investigated along with RF MEMS switches and the results are also presented. Investigations were carried out to check the efficiency of the antenna in the wireless powering domain. The antenna was placed in a concrete block and its result comparison to that of a dipole antenna is also presented in this paper.
Matsumura, Takeshi; Esashi, Masayoshi; Harada, Hiroshi; Tanaka, Shuji
For future mobile phones based on cognitive radio technology, a compact multi-band RF front-end architecture is strongly required and an integrated multi-band RF filter bank is a key component in it. Contour-mode resonators are receiving increased attention for a multi-band filter solution, because its resonant frequency is mainly determined by its size and shape, which are defined by lithography. However, spurious responses including flexural vibration are also excited due to its thin structure. To improve resonator performance and suppress spurious modes, visual observation with a laser probe system is very effective. In this paper, we have prototyped a mechanically-coupled disk-array filter, which consists of a Si disk and 2 disk-type resonators of higher-order wine-glass mode, and observed its vibration modes using a high-frequency laser-Doppler vibrometer (UHF-120, Polytec, Inc.). As a result, it was confirmed that higher order wine-glass mode vibration included a compound displacement, and that its out-of-plane vibration amplitude was much smaller than other flexural spurious modes. The observed vibration modes were compared with FEM (Finite Element Method) simulation results. In addition, it was also confirmed that the fabrication error, e.g. miss-alignment, induced asymmetric vibration.
Quan, Wei; Li, Yang; Li, Rujie; Shang, Huining; Fang, Zishan; Qin, Jie; Wan, Shuangai
2016-04-01
We propose a far off-resonance laser frequency stabilization method by using multipass cells in Rb Faraday rotation spectroscopy. Based on the detuning equation, if multipass cells with several meters optical path length are used in the conventional Faraday spectroscopy, the detuning of the lock point can be extended much further from the alkali metal resonance. A plate beam splitter was used to generate two different Faraday signals at the same time. The transmitted optical path length was L=50 mm and the reflected optical path length was 2L=100 mm. When the optical path length doubled, the detuning of the lock points moved further away from the atomic resonance. The temperature dependence of the detuning of the lock point was also analyzed. A temperature-insensitive lock point was found near resonance when the cell temperature was between 110°C and 130°C. We achieved an rms fluctuation of 0.9 MHz/23 h at a detuning of 0.5 GHz. A frequency drift of 16 MHz/h at a detuning of -5.6 GHz and 4 MHz/h at a detuning of -5.2 GHz were also obtained for the transmitted and reflected light Faraday signal.
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.
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.
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...... wind farm in Sweden and solar radiation data in Aberdeen (United Kingdom) was used in order to examine the performance of the proposed novel controller. A comparison is made between the achieved results of Optimal Fuzzy-PI (OFPI) controller and those of Optimal Interval Type II Fuzzy-PI (IT2FPI...... 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...
Redistribution of light frequency by multiple scattering in a resonant atomic vapor
Carvalho, J C de A; Oriá, M; Chevrollier, M; de Silans, T Passerat
2015-01-01
The propagation of light in a resonant atomic vapor can \\textit{a priori} be thought of as a multiple scattering process, in which each scattering event redistributes both the direction and the frequency of the photons. Particularly, the frequency redistribution may result in L\\'evy flights of photons, directly affecting the transport properties of light in a resonant atomic vapor and turning this propagation into a superdifusion process. Here, we report on a Monte-Carlo simulation developed to study the evolution of the spectrum of the light in a resonant thermal vapor. We observe the gradual change of the spectrum and its convergence towards a regime of Complete Frequency Redistribution as the number of scattering events increases. We also analyse the probability density function of the step length of photons between emissions and reabsorptions in the vapor, which governs the statistics of the light diffusion. We observe two different regime in the light transport: superdiffusive when the vapor is excited n...
Vocal tract motor patterns and resonance during constant frequency song: the white-throated sparrow.
Riede, Tobias; Suthers, Roderick A
2009-02-01
Bird song is a complex behavior that requires the coordination of several motor systems. Sound is produced in the syrinx and then modified by the upper vocal tract. Movements of the hyoid skeleton have been shown in the northern cardinal (Cardinalis cardinalis) to be extensively involved in forming an oropharyngeal-esophageal cavity (OEC), which contributes a major resonance to the vocal tract transfer function. Here we report that a similar relationship exists between the volume of the OEC and the fundamental frequency in the white-throated sparrow (Zonotrichia albicollis) whose song, unlike that of the cardinal, consists of a series of almost constant frequency notes. Cineradiography of singing sparrows shows that the oropharyngeal cavity and cranial end of the esophagus expand abruptly at the start of each note and maintain a relatively constant volume until the end of the note. Computation of the vocal tract transfer function suggests a major resonance of the OEC follows the fundamental frequency, making sound transmission more efficient. The presence of similar prominent song-related vocal tract motor patterns in two Oscine families suggests that the active control of the vocal tract resonance by varying the volume of the OEC may be widespread in songbirds.
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.
Resonant frequency of mass-loaded membranes for vibration energy harvesting applications
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Lin Dong
2015-08-01
Full Text Available Vibration based energy harvesting has been widely investigated to target ambient vibration sources as a means to generate small amounts of electrical energy. While cantilever-based geometries have been pursued frequently in the literature, here membrane-based geometries for the energy harvesting device is considered, with the effects of an added mass and tension on the effective resonant frequency of the membranes studied. An analytical model is developed to describe the vibration response for a circular membrane with added mass structure, with the results closely agreeing with finite element simulation in ANSYS. A complementary study of square membranes loaded with a central mass shows analogous behavior. The analytical model is then used to interpret the experimentally observed shift in resonance frequency of a circular membrane with a proof mass. The impact of membrane tension and central proof mass on the resonant frequency of the membrane suggests that this approach may be used as a tuning method to optimize the response of membrane-based designs for maximum power output for vibration energy harvesting applications.
Fundamental frequencies and resonances from eccentric and precessing binary black hole inspirals
Lewis, Adam G M; Pfeiffer, Harald P
2016-01-01
Binary black holes which are both eccentric and undergo precession remain unexplored in numerical simulations. We present simulations of such systems which cover about 50 orbits at comparatively high mass ratios 5 and 7. The configurations correspond to the generic motion of a nonspinning body in a Kerr spacetime, and are chosen to study the transition from finite mass-ratio inspirals to point particle motion in Kerr. We develop techniques to extract analogs of the three fundamental frequencies of Kerr geodesics, compare our frequencies to those of Kerr, and show that the differences are consistent with self-force corrections entering at first order in mass ratio. This analysis also locates orbital resonances where the ratios of our frequencies take rational values. At the considered mass ratios, the binaries pass through resonances in one to two resonant cycles, and we find no discernible effects on the orbital evolution. We also compute the decay of eccentricity during the inspiral and find good agreement w...
Adaptive filtering methods for identifying cross-frequency couplings in human EEG.
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Jérôme Van Zaen
Full Text Available Oscillations have been increasingly recognized as a core property of neural responses that contribute to spontaneous, induced, and evoked activities within and between individual neurons and neural ensembles. They are considered as a prominent mechanism for information processing within and communication between brain areas. More recently, it has been proposed that interactions between periodic components at different frequencies, known as cross-frequency couplings, may support the integration of neuronal oscillations at different temporal and spatial scales. The present study details methods based on an adaptive frequency tracking approach that improve the quantification and statistical analysis of oscillatory components and cross-frequency couplings. This approach allows for time-varying instantaneous frequency, which is particularly important when measuring phase interactions between components. We compared this adaptive approach to traditional band-pass filters in their measurement of phase-amplitude and phase-phase cross-frequency couplings. Evaluations were performed with synthetic signals and EEG data recorded from healthy humans performing an illusory contour discrimination task. First, the synthetic signals in conjunction with Monte Carlo simulations highlighted two desirable features of the proposed algorithm vs. classical filter-bank approaches: resilience to broad-band noise and oscillatory interference. Second, the analyses with real EEG signals revealed statistically more robust effects (i.e. improved sensitivity when using an adaptive frequency tracking framework, particularly when identifying phase-amplitude couplings. This was further confirmed after generating surrogate signals from the real EEG data. Adaptive frequency tracking appears to improve the measurements of cross-frequency couplings through precise extraction of neuronal oscillations.
Adaptive filtering methods for identifying cross-frequency couplings in human EEG.
Van Zaen, Jérôme; Murray, Micah M; Meuli, Reto A; Vesin, Jean-Marc
2013-01-01
Oscillations have been increasingly recognized as a core property of neural responses that contribute to spontaneous, induced, and evoked activities within and between individual neurons and neural ensembles. They are considered as a prominent mechanism for information processing within and communication between brain areas. More recently, it has been proposed that interactions between periodic components at different frequencies, known as cross-frequency couplings, may support the integration of neuronal oscillations at different temporal and spatial scales. The present study details methods based on an adaptive frequency tracking approach that improve the quantification and statistical analysis of oscillatory components and cross-frequency couplings. This approach allows for time-varying instantaneous frequency, which is particularly important when measuring phase interactions between components. We compared this adaptive approach to traditional band-pass filters in their measurement of phase-amplitude and phase-phase cross-frequency couplings. Evaluations were performed with synthetic signals and EEG data recorded from healthy humans performing an illusory contour discrimination task. First, the synthetic signals in conjunction with Monte Carlo simulations highlighted two desirable features of the proposed algorithm vs. classical filter-bank approaches: resilience to broad-band noise and oscillatory interference. Second, the analyses with real EEG signals revealed statistically more robust effects (i.e. improved sensitivity) when using an adaptive frequency tracking framework, particularly when identifying phase-amplitude couplings. This was further confirmed after generating surrogate signals from the real EEG data. Adaptive frequency tracking appears to improve the measurements of cross-frequency couplings through precise extraction of neuronal oscillations.
Rossini, Aaron J.; Hamaed, Hiyam; Schurko, Robert W.
2010-09-01
The acquisition of nuclear quadrupole resonance (NQR) spectra with wideband uniform rate and smooth truncation (WURST) pulses is investigated. 75As and 35Cl NQR spectra acquired with the WURST echo sequence are compared to those acquired with standard Hahn-echo sequences and echo sequences which employ composite refocusing pulses. The utility of WURST pulses for locating NQR resonances of unknown frequency is investigated by monitoring the integrated intensity and signal to noise of 35Cl and 75As NQR spectra acquired with transmitter offsets of several hundreds kilohertz from the resonance frequencies. The WURST echo sequence is demonstrated to possess superior excitation bandwidths in comparison to the pulse sequences which employ conventional monochromatic rectangular pulses. The superior excitation bandwidths of the WURST pulses allows for differences in the characteristic impedance of the receiving and excitation circuits of the spectrometer to be detected. Impedance mismatches have previously been reported by Marion and Desvaux [D.J.Y. Marion, H. Desvaux, J. Magn. Reson. (2008) 193(1) 153-157] and Muller et al. [M. Nausner, J. Schlagnitweit, V. Smrecki, X. Yang, A. Jerschow, N. Muller, J. Magn. Reson. (2009) 198(1) 73-79]. In this regard, WURST pulse sequences may afford an efficient new method for experimentally detecting impedance mismatches between receiving and excitation circuits, allowing for the optimization of solids and solution NMR and NQR spectrometer systems. The use of the Carr-Purcell Meiboom-Gill (CPMG) pulse sequence for signal enhancement of NQR spectra acquired with WURST pulses and conventional pulses is also investigated. Finally, the utility of WURST pulses for the acquisition of wideline NQR spectra is demonstrated by acquiring part of the 63/65Cu NQR spectrum of CuCN.
Generation of THz frequency using PANDA ring resonator for THz imaging
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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
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.
Input impedance matching of acoustic transducers operating at off-resonant frequencies.
Son, Kyu Tak; Lee, Chin C
2010-12-01
The input impedance matching technique of acoustic transducers at off-resonant frequencies is reported. It uses an inherent impedance property of transducers and thus does not need an external electric matching circuit or extra acoustic matching section. The input electrical equivalent circuit includes a radiation component and a dielectric capacitor. The radiation component consists of a radiation resistance and a radiation reactance. The total reactance is the sum of the radiation reactance and the dielectric capacitive reactance. This reactance becomes zero at two frequencies where the impedance is real. The transducer size can be properly chosen so that the impedance at one of the zero-crossing frequencies is close to 50 Ω, the output impedance of signal generators. At this off-resonant operating frequency, the reflection coefficient of the transducer is minimized without using any matching circuit. Other than the size, the impedance can also be fine tuned by adjusting the thickness of material that bonds the transducer plate to the substrates. The acoustic impedance of the substrate and that of the bonding material can also be used as design elements in the transducer structure to achieve better transducer matching. Lead titanate piezoelectric plates were bonded on Lucite, liquid crystal polymer (LCP), and bismuth (Bi) substrates to produce various transducer structures. Their input impedance was simulated using a transducer model and compared with measured values to illustrate the matching principle.
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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.
Resonant tube for measurement of sound absorption in gases at low frequency/pressure ratios
Zuckerwar, A. J.; Griffin, W. A.
1980-01-01
The paper describes a resonant tube for measuring sound absorption in gases, with specific emphasis on the vibrational relaxation peak of N2, over a range of frequency/pressure ratios from 0.1 to 2500 Hz/atm. The experimental background losses measured in argon agree with the theoretical wall losses except at few isolated frequencies. Rigid cavity terminations, external excitation, and a differential technique of background evaluation were used to minimize spurious contributions to the background losses. Room temperature measurements of sound absorption in binary mixtures of N2-CO2 in which both components are excitable resulted in the maximum frequency/pressure ratio in Hz/atm of 0.063 + 123m for the N2 vibrational relaxation peak, where m is mole percent of added CO2; the maximum ratio for the CO2 peak was 34,500 268m where m is mole percent of added N2.
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S. Keyrouz
2016-01-01
Full Text Available An up-to-date literature overview on relevant approaches for controlling circuital characteristics and radiation properties of dielectric resonator antennas (DRAs is presented. The main advantages of DRAs are discussed in detail, while reviewing the most effective techniques for antenna feeding as well as for size reduction. Furthermore, advanced design solutions for enhancing the realized gain of individual DRAs are investigated. In this way, guidance is provided to radio frequency (RF front-end designers in the selection of different antenna topologies useful to achieve the required antenna performance in terms of frequency response, gain, and polarization. Particular attention is put in the analysis of the progress which is being made in the application of DRA technology at millimeter-wave frequencies.
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.
Jia, Y.; Yan, J.; Soga, K.; Seshia, A. A.
2013-12-01
The mechanical amplification effect of parametric resonance has the potential to outperform direct resonance by over an order of magnitude in terms of power output. However, the excitation must first overcome the damping-dependent initiation threshold amplitude prior to accessing this more profitable region. In addition to activating the principal (1st order) parametric resonance at twice the natural frequency ω0, higher orders of parametric resonance may be accessed when the excitation frequency is in the vicinity of 2ω0/n for integer n. Together with the passive design approaches previously developed to reduce the initiation threshold to access the principal parametric resonance, vacuum packaging (< 10 torr) is employed to further reduce the threshold and unveil the higher orders. A vacuum packaged MEMS electrostatic harvester (0.278 mm3) exhibited 4 and 5 parametric resonance peaks at room pressure and vacuum respectively when scanned up to 10 g. At 5.1 ms-2, a peak power output of 20.8 nW and 166 nW is recorded for direct and principal parametric resonance respectively at atmospheric pressure; while a peak power output of 60.9 nW and 324 nW is observed for the respective resonant peaks in vacuum. Additionally, unlike direct resonance, the operational frequency bandwidth of parametric resonance broadens with lower damping.
A Prospective Study on Algorithms Adapted to the Spatial Frequency in Tomography
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Vincent Israel-Jost
2006-01-01
Full Text Available The use of iterative algorithms in tomographic reconstruction always leads to a frequency adapted rate of convergence in that low frequencies are accurately reconstructed after a few iterations, while high frequencies sometimes require many more computations. In this paper, we propose to build frequency adapted (FA algorithms based on a condition of incomplete backprojection and propose an FA simultaneous algebraic reconstruction technique (FA-SART algorithm as an example. The results obtained with the FA-SART algorithm demonstrate a very fast convergence on a highly detailed phantom when compared to the original SART algorithm. Though the use of such an FA algorithm may seem difficult, we specify in which case it is relevant and propose several ways to improve the reconstruction process with FA algorithms.
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.
Hynds, Taylor D.; Kauffman, Jeffrey L.
2015-04-01
Piezoelectric-based vibration energy harvesting is of interest in a wide range of applications, and a number of harvesting schemes have been proposed and studied { primarily when operating under steady state conditions. However, energy harvesting behavior is rarely studied in systems with transient excitations. This paper will work to develop an understanding of this behavior within the context of a particular vibration reduction technique, resonance frequency detuning. Resonance frequency detuning provides a method of reducing mechanical response at structural resonances as the excitation frequency sweeps through a given range. This technique relies on switching the stiffness state of a structure at optimal times to detune its resonance frequency from that of the excitation. This paper examines how this optimal switch may be triggered in terms of the energy harvested, developing a normalized optimal switch energy that is independent of the open- and short-circuit resistances. Here the open- and short-circuit shunt resistances refer to imposed conditions that approximate the open- and short-circuit conditions, via high and low resistance shunts. These conditions are practically necessary to harvest the small amounts of power needed to switch stiffness states, as open-circuit and closed-circuit refer to infinite resistance and zero resistance, respectively, and therefore no energy passes through the harvesting circuit. The limiting stiffness states are then defined by these open- and short-circuit resistances. The optimal switch energy is studied over a range of sweep rates, damping ratios, and coupling coefficients; it is found to increase with the coupling coefficient and decrease as the sweep rate and damping ratio increase, behavior which is intuitive. Higher coupling means more energy is converted by the piezoelectric material, and therefore more energy is harvested in a given time; an increased sweep rate means resonance is reached sooner, and there will less
Keller, T.; Hanzo, L.
2000-01-01
A historical perspective of orthogonal frequency-division multiplexing (OFDM) is given with reference to its literature. Its advantages and disadvantages are reviewed, and its performance is characterized over highly dispersive channels. The effects of both time- and frequency-domain synchronization errors are quantified, and a range of solutions proposed in the recent literature are re-viewed. One of the main objectives of this review is to highlight the recent thinking behind adaptive bit a...
Non-destructive testing of ceramic balls using high frequency ultrasonic resonance spectroscopy.
Petit, S; Duquennoy, M; Ouaftouh, M; Deneuville, F; Ourak, M; Desvaux, S
2005-12-01
Although ceramic balls are used more and more for bearings in the aerospace and space industries, defects in this type of ceramic material could be dangerous, particularly if such defects are located close to the surface. In this paper, we propose a non-destructive testing method for silicon nitride balls, based on ultrasonic resonance spectroscopy. Through the theoretical study of their elastic vibrations, it is possible to characterize the balls using a vibration mode that is similar to surface wave propagation. The proposed methodology can both excite spheroidal vibrations in the ceramic balls and detect such vibrations over a large frequency range. Studying their resonance spectrums allows the balls' elastic parameters be characterized. Ours is an original method that can quickly estimate the velocity of surface waves using high frequency resonances, which permits surface and sub-surface areas to be tested specifically. Two applications are described in this paper. Both use velocity measurements to achieve their different goals, the first to differentiate between flawless balls from different manufacturing processes, and the second to detect small defects, such as cracks. Our method is rapid and permits the entire ceramic ball to be tested in an industrial context.
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.
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.
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.
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V. V. Dzyubenko
1987-12-01
Full Text Available The analysis of the quality of the parametric frequency stabilization of solid state microwave generators in the four-pole through-inclusion of stabilizing resonator absorbing load. Lredlozhena technique optimal setting generators.
V. V. Dzyubenko; E. A. Zaritskaya; E. A. Machusskii
1987-01-01
The analysis of the quality of the parametric frequency stabilization of solid state microwave generators in the four-pole through-inclusion of stabilizing resonator absorbing load. Lredlozhena technique optimal setting generators.
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.
Nikolopoulos, G M
2012-01-01
We study the effects of field fluctuations on the total yields of Auger electrons, obtained in the excitation of neutral atoms to a core-excited state by means of short-wavelength free-electron-laser pulses. Beginning with a self-contained analysis of the statistical properties of fluctuating free-electron-laser pulses, we analyse separately and in detail the cases of single and double Auger resonances, focusing on fundamental phenomena such as power broadening and ac Stark (Autler-Townes) splitting. In certain cases, field fluctuations are shown to influence dramatically the frequency response of the resonances, whereas in other cases the signal obtained may convey information about the bandwidth of the radiation as well as the dipole moment between Auger states.
Analysis and Active Damping of Multiple High Frequency Resonances in DFIG System
DEFF Research Database (Denmark)
Song, Yipeng; Blaabjerg, Frede; Wang, Xiongfei
2017-01-01
As the wind power generation develops, the Doubly Fed Induction Generator (DFIG) based wind power system are more and more likely to operate in the emerging weak network rather than the conventional stiff network. Due to the comparatively large impedance of the weak network than the stiff grid......, the DFIG system may be subject to the resonances due to the impedance interaction between the DFIG system and the weak network. Especially, when connected to a series π sections weak network, the Multiple High Frequency Resonances (MHFR) may occur and require careful studies. The impedance modeling...... of the DFIG system and the series π sections weak network is firstly demonstrated in this paper. Then, due to the multiple magnitude peaks of the series π sections of the weak network, the MHFR will be produced and can be theoretically explained based on the impedance modeling results. For the purpose...
A Switched Capacitor Based AC/DC Resonant Converter for High Frequency AC Power Generation
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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.
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...
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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.
Loures, Cristian Redondo; Faccio, Daniele; Biancalana, Fabio
2015-01-01
Starting from the infinite-dimensional Ikeda map, we derive an extended temporal Lugiato-Lefever equation that may account for the effects of the conjugate electromagnetic fields (also called `negative frequency fields'). In the presence of nonlinearity in a ring cavity, these fields lead to new forms of modulational instability and resonant radiations. Numerical simulations based on the new extended Lugiato-Lefever model show that the negative-frequency resonant radiations emitted by ultrash...
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.
Adaptive stochastic resonance method for weak signal detection based on particle swarm optimization
Institute of Scientific and Technical Information of China (English)
XING; Hongyan; ZHANG; Qiang; LU; Chunxia
2015-01-01
In order to solve the parameter adjustment problems of adaptive stochastic resonance system in the areas of weak signal detection,this article presents a new method to enhance the detection efficiency and availability in the system of two-dimensional Duffing based on particle swarm optimization.First,the influence of different parameters on the detection performance is analyzed respectively.The correlation between parameter adjustment and stochastic resonance effect is also discussed and converted to the problem of multi-parameter optimization.Second,the experiments including typical system and sea clutter data are conducted to verify the effect of the proposed method.Results show that the proposed method is highly effective to detect weak signal from chaotic background,and enhance the output SNR greatly.
High-Frequency Intermuscular Coherence between Arm Muscles during Robot-Mediated Motor Adaptation
Pizzamiglio, Sara; De Lillo, Martina; Naeem, Usman; Abdalla, Hassan; Turner, Duncan L.
2017-01-01
Adaptation of arm reaching in a novel force field involves co-contraction of upper limb muscles, but it is not known how the co-ordination of multiple muscle activation is orchestrated. We have used intermuscular coherence (IMC) to test whether a coherent intermuscular coupling between muscle pairs is responsible for novel patterns of activation during adaptation of reaching in a force field. Subjects (N = 16) performed reaching trials during a null force field, then during a velocity-dependent force field and then again during a null force field. Reaching trajectory error increased during early adaptation to the force-field and subsequently decreased during later adaptation. Co-contraction in the majority of all possible muscle pairs also increased during early adaptation and decreased during later adaptation. In contrast, IMC increased during later adaptation and only in a subset of muscle pairs. IMC consistently occurred in frequencies between ~40–100 Hz and during the period of arm movement, suggesting that a coherent intermuscular coupling between those muscles contributing to adaptation enable a reduction in wasteful co-contraction and energetic cost during reaching. PMID:28119620
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Fleury, W.H.; Rosinger, H.E.; Ritchie, I.G.
1975-09-01
A set of computer programs for the calculation of the flexural and torsional resonant frequencies of rectangular section bars of materials of orthotropic or high symmetry are described. The calculations are used in the experimental determination and verification of the elastic constants of anisotropic materials. The simple finite element technique employed separates the inertial and elastic properties of the beam element into station and field transfer matrices respectively. It includes the Timoshenko beam corrections for flexure and Lekhnitskii's theory for torsion-flexure coupling. The programs also calculate the vibration shapes and surface nodal contours or Chladni figures of the vibration modes. (auth)
Umarji, Govind; Qureshi, Nilam; Gosavi, Suresh; Mulik, Uttam; Kulkarni, Atul; Kim, Taesung; Amalnerkar, Dinesh
2017-02-01
In conventional thick-film technology, there are often problems associated with poor edges, rough surfaces, and reproducibility due to process limitations, especially for high-frequency applications. These difficulties can be circumvented by using thin-film technology, but process cost and complexity remain major concerns. In this context, photopatternable thick-film technology can offer a viable alternative due to its Newtonian rheology, which can facilitate formation of the required sharp edges. We present herein a unique attempt to formulate a photopatternable silver paste with organic (photosensitive polymer) to inorganic (silver and glass) ratio of 30:70, developed in-house by us for fabrication of thick-film-based ring resonator and band-pass filter components. The ring resonator and band-pass component structures were realized by exposing screen-printed film to ultraviolet light at wavelength of 315 nm to 400 nm for 30 s to crosslink the photosensitive polymer. The pattern was subsequently developed using 1% sodium carbonate aqueous solution. For comparison, conventional silver and silver-palladium thick films were produced using in-house formulations. The surface topology and microstructural features were examined by stereomicroscopy and scanning electron microscopy. The smoothness and edge definition of the film were assessed by profilometry. The resistivity of the samples was observed and remained in the range from 3.4 μΩ cm to 3.6 μΩ cm. The electrical properties were compared by measuring the insertion loss characteristics. The results revealed that the ring resonator fabricated using the photopatternable silver paste exhibited better high-frequency properties compared with components based on conventional silver or silver-palladium paste, especially in terms of the resonant frequency of 10.1 GHz (versus 10 GHz designed) with bandwidth of 80 MHz. Additionally, the band-pass filter fabricated using the photopatternable silver paste displayed better
Sakalli, I.
2016-10-01
Charged massive scalar field perturbations are studied in the gravitational, electromagnetic, dilaton, and axion fields of rotating linear dilaton black holes. In this geometry, we separate the covariant Klein-Gordon equation into radial and angular parts and obtain the exact solutions of both the equations in terms of the confluent Heun functions. Using the radial solution, we study the problems of resonant frequencies, entropy/area quantization, and greybody factor. We also analyze the behavior of the wave solutions near the event horizon of the rotating linear dilaton black hole and derive its Hawking temperature via the Damour-Ruffini-Sannan method.
High frequency bulk resonators for bio/chemical diagnostics and monitoring applications
DEFF Research Database (Denmark)
Cagliani, Alberto
In the environmental monitoring eld there is a vast variety of possible applications for microfabricated MEMS sensors. As an example, a network of miniaturized sensors could detect toxic gases, harmful airbornes, explosives in air or, in liquid, monitor the quality of drinking water...... is by monitoring the target mass, that is continuously deposited or removed from the sensor's surface, while the sensor's structure vibrates in resonance. This thesis presents the development of MEMS mass sensors based on mechanical microresonators in the very high frequency range 12-132 MHz. This devices can...
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.
A model of reverse spike frequency adaptation and repetitive firing of subthalamic nucleus neurons.
Wilson, Charles J; Weyrick, Angela; Terman, David; Hallworth, Nicholas E; Bevan, Mark D
2004-05-01
Subthalamic nucleus neurons exhibit reverse spike-frequency adaptation. This occurs only at firing rates of 20-50 spikes/s and higher. Over this same frequency range, there is an increase in the steady-state frequency-intensity (F-I) curve's slope (the secondary range). Specific blockade of high-voltage activated calcium currents reduced the F-I curve slope and reverse adaptation. Blockade of calcium-dependent potassium current enhanced secondary range firing. A simple model that exhibited these properties used spike-triggered conductances similar to those in subthalamic neurons. It showed: 1) Nonaccumulating spike afterhyperpolarizations produce positively accelerating F-I curves and spike-frequency adaptation that is complete after the second spike. 2) Combinations of accumulating aftercurrents result in a linear F-I curve, whose slope depends on the relative contributions of inward and outward currents. Spike-frequency adaptation can be gradual. 3) With both accumulating and nonaccumulating aftercurrents, primary and secondary ranges will be present in the F-I curve. The slope of the primary range is determined by the nonaccumulating conductance; the accumulating conductances govern the secondary range. The transition is determined by the relative strengths of accumulating and nonaccumulating currents. 4) Spike-threshold accommodation contributes to the secondary range, reducing its slope at high firing rates. Threshold accommodation can stabilize firing when inward aftercurrents exceed outward ones. 5) Steady-state reverse adaptation results when accumulated inward aftercurrents exceed outward ones. This requires spike-threshold accommodation. Transient speedup arises when inward currents are smaller than outward ones at steady state, but accumulate more rapidly. 6) The same mechanisms alter firing in response to irregular patterns of synaptic conductances, as cell excitability fluctuates with changes in firing rate.
High Frequency Soft Switching Of PWM Boost Converter Using Auxiliary Resonant Circuit
Directory of Open Access Journals (Sweden)
C. P. Sai Kiran
2014-10-01
Full Text Available 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 increases. This restricts the use of PWM technique. New Zero Voltage Transition-Zero Current Transition (ZVT-ZCT PWM converter equipped with the snubber provides the most desirable features of both ZVT and ZCT converters presented previously. Moreover all semiconductors devices operate with soft switching and hence losses are reduced.
Spin-torque diode radio-frequency detector with voltage tuned resonance
Energy Technology Data Exchange (ETDEWEB)
Skowroński, Witold, E-mail: skowron@agh.edu.pl; Frankowski, Marek; Stobiecki, Tomasz [AGH University of Science and Technology, Department of Electronics, Al. Mickiewicza 30, 30-059 Kraków (Poland); Wrona, Jerzy [AGH University of Science and Technology, Department of Electronics, Al. Mickiewicza 30, 30-059 Kraków (Poland); Singulus Technologies, Kahl am Main 63796 (Germany); Ogrodnik, Piotr [Faculty of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warsaw (Poland); AGH University of Science and Technology, Department of Electronics, Al. Mickiewicza 30, 30-059 Kraków (Poland); Barnaś, Józef [Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań (Poland); Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań (Poland)
2014-08-18
We report on a voltage-tunable radio-frequency (RF) detector based on a magnetic tunnel junction (MTJ). The spin-torque diode effect is used to excite and/or detect RF oscillations in the magnetic free layer of the MTJ. In order to reduce the overall in-plane magnetic anisotropy of the free layer, we take advantage of the perpendicular magnetic anisotropy at the interface between ferromagnetic and insulating layers. The applied bias voltage is shown to have a significant influence on the magnetic anisotropy, and thus on the resonance frequency of the device. This influence also depends on the voltage polarity. The obtained results are accounted for in terms of the interplay of spin-transfer-torque and voltage-controlled magnetic anisotropy effects.
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.
Clark, W. G.; Hanson, M. E.; Lefloch, F.; Ségransan, P.
1995-03-01
A novel method of Fourier transform spectroscopy of the transient signals from wide, inhomogeneously broadened magnetic resonance spectra is described and analyzed. It has the advantages of high resolution, high sensitivity, and freedom from the distortions introduced by the finite amplitude of the pulsed rf magnetic field and the finite bandwidth of the receiving system. It consists of recording the transient signal at a series of magnetic fields, shifting the frequency of the transient by the corresponding field step for each point, and summing the corresponding Fourier transformed signals. Although the primary emphasis is on pulsed NMR, the analysis also applies to pulsed ESR. Criteria for the range and step interval of the magnetic field variation are discussed. The accuracy and sensitivity of the method are compared with earlier methods of spin echo spectroscopy. A description of the corresponding measurement of NQR, NMR, and ESR spectra obtained by stepping the frequency of the spectrometer is also presented.
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.
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
Analysis of Power Quality Signals Using an Adaptive Time-Frequency Distribution
Directory of Open Access Journals (Sweden)
Nabeel A. Khan
2016-11-01
Full Text Available Spikes frequently occur in power quality (PQ disturbance signals due to various causes such as switching of the inductive loads and the energization of the capacitor bank. Such signals are difficult to analyze using existing time-frequency (TF methods as these signals have two orthogonal directions in a TF plane. To address this issue, this paper proposes an adaptive TF distribution (TFD for the analysis of PQ signals. In the proposed adaptive method, the smoothing kernel’s direction is locally adapted based on the direction of energy in the joint TF domain, and hence an improved TF resolution can be obtained. Furthermore, the performance of the proposed adaptive technique in analyzing electrical PQ is thoroughly studied for both synthetic and real world electrical power signals with the help of extensive simulations. The simulation results (specially for empirical data indicate that the adaptive TFD method achieves high energy concentration in the TF domain for signals composed of tones and spikes. Moreover, the local adaptation of the smoothing kernel in the adaptive TFD enables the extraction of TF signature of spikes from TF images, which further helps in measuring the energy of spikes in a given signal. This new measure can be used to both detect the spikes as well as to quantify the extent of distortion caused by the spikes in a given signal.
Nellutla, Saritha; Nori, Sudhakar; Singamaneni, Srinivasa R.; Prater, John T.; Narayan, Jagdish; Smirnov, Alex I.
2016-12-01
Partially aligned nickel nanocubes were grown epitaxially in a diamagnetic magnesium oxide (MgO:Ni) host and studied by a continuous wave ferromagnetic resonance (FMR) spectroscopy at the X-band (9.5 GHz) from ca. 117 to 458 K and then at room temperature for multiple external magnetic fields/resonant frequencies from 9.5 to 330 GHz. In contrast to conventional magnetic susceptibility studies that provided data on the bulk magnetization, the FMR spectra revealed the presence of three different types of magnetic Ni nanocubes in the sample. Specifically, three different ferromagnetic resonances were observed in the X-band spectra: a line 1 assigned to large nickel nanocubes, a line 2 corresponding to the nanocubes exhibiting saturated magnetization even at ca. 0.3 T field, and a high field line 3 (geff ˜ 6.2) tentatively assigned to small nickel nanocubes likely having their hard magnetization axis aligned along or close to the direction of the external magnetic field. Based on the analysis of FMR data, the latter nanocubes possess an anisotropic internal magnetic field of at least ˜1.0 T in magnitude.
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.
Adaptive high-frequency information fusion algorithm of radar and optical images
Wang, Yiding; Qin, Shuai
2011-12-01
An adaptive High-frequency Information Fusion Algorithm of Radar and Optical Images is proposed in this paper, in order to improve the resolution of the radar image and reserve more radar information. Firstly, Hough Transform is adopted in the process of low-resolution radar image and high-resolution optical image registration. The implicit linear information is extracted from two different heterogeneous images for better result. Then NSCT transform is used for decomposition and fusion. In different decomposition layers or in the same layer with different directions, fusion rules are adaptive for the high-frequency information of images. The ratio values of high frequency information entropy, variance, gradient and edge strength are calculated after NSCT decomposition. High frequency information entropy, variance, gradient or edge strength, which has the smallest ratio value, is selected as an optimal rule for regional fusion. High-frequency information of radar image could be better retained, at the same time the low-frequency information of optical image also could be remained. Experimental results showed that our approach performs better than those methods with single fusion rule.
Energy Technology Data Exchange (ETDEWEB)
Ooe, Hiroaki; Sakuishi, Tatsuya; Arai, Toyoko, E-mail: arai@staff.kanazawa-u.ac.jp [Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192 (Japan); Nogami, Makoto; Tomitori, Masahiko [Japan Advanced Institute of Science and Technology, Nomi, Ishikawa 923-1292 (Japan)
2014-07-28
Based on a two-prong type quartz tuning fork, a force sensor with a high Q factor, which we call a retuned fork sensor, was developed for non-contact atomic force microscopy (nc-AFM) with atomic resolution. By cutting a small notch and attaching an AFM tip to one prong, its resonance frequency can be retuned to that of the other intact prong. In balancing the two prongs in this manner, a high Q factor (>50 000 in ultrahigh vacuum) is obtained for the sensor. An atomic resolution image of the Si(111)-7 × 7 surface was demonstrated using an nc-AFM with the sensor. The dependence of the Q factor on resonance frequency of the sensor and the long-range force between tip and sample were measured and analyzed in view of the various dissipation channels. Dissipation in the signal detection circuit turned out to be mainly limited by the total Q factor of the nc-AFM system.
DNA Hybridization Detection Based on Resonance Frequency Readout in Graphene on Au SPR Biosensor
Directory of Open Access Journals (Sweden)
Md. Biplob Hossain
2016-01-01
Full Text Available This paper demonstrates a numerical modeling of surface plasmon resonance (SPR biosensor for detecting DNA hybridization by recording the resonance frequency characteristics (RFC. The proposed sensor is designed based on graphene material as biomolecular recognition elements (BRE and the sharp SPR curve of gold (Au. Numerical analysis shows that the variation of RFC for mismatched DNA strands is quiet negligible whereas that for complementary DNA strands is considerably countable. Here, graphene is used to perform faster immobilization between target DNA and probe DNA. The usage of graphene also changes the RFC that ensure hybridization of DNA event by utilizing its optochemical property. In addition, proposed sensor successfully distinguishes between hybridization and single-nucleotide polymorphisms (SNP by observing the variation level of RFC and maximum transmittance. Therefore, the proposed frequency readout based SPR sensor could potentially open a new window of detection for biomolecular interactions. We also highlight the advantage of using graphene sublayer by performing the sensitivity analysis. Sandwiching of each graphene sublayer enhances 95% sensitivity comparing with conventional SPR sensor.
Range Detection of the Extremely Low-Frequency Magnetic Field Produced by Laptop's AC Adapter
Brodić, Darko; Amelio, Alessia
2017-02-01
Human exposure to extremely low frequency magnetic field represents a risk to their health. This paper takes into consideration the level of an extremely low-frequency magnetic field between 30 and 300 Hz emitted by an AC laptop adapter. The experiment consists of testing 17 different AC adapters for laptops. During the testing, laptops are operated in a normal operating conditions as well as under heavy load. The magnetic field measurement is conducted in the area around the AC adapter. Obtained data is evaluated according to the critical level of the magnetic field proposed by safety standards. Furthermore, data is classified by a K-medians method in order to determine the critical levels of the magnetic field exposure in the nearby area of the AC adapter. Obtained classifications are evaluated according to safety standards, giving a critical analysis of magnetic field areas at risk. Due to emission of a very strong magnetic field in certain areas, a recommendation for safety use of the AC adapter is proposed.
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.
Conchouso, David
2016-06-28
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. © 2016 The Royal Society of Chemistry.
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.
Interaction of the Electromagnetic p-Wave with Thin Metal Film in the Field of Resonant Frequencies
Latyshev, A V
2011-01-01
It is shown that for thin metallic films thickness of which does not exceed thickness of skin layer, the problem allows analytical solution. In the field of resonant frequencies the analysis of dependence of coefficients of transmission, reflection and absorbtion on an electromagnetic wave is carried out. Dependence on pitch angle, thickness of the layer and coefficient of specular reflection and on effective electron collision frequency is carried out. The formula for contactless determination (calculation) of a thickness of a film by observable resonant frequencies is deduced.
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.
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.
1977-05-01
and 6() in place of the corresponding resonance quantities. In the limit o - I (CL - o), the load frequencies approach the antiresonance frequencies...while the limit a o (CL c) reduces the frequencies to the resonances. 2 Cu. Y+ _II ZL w NOW"z CZ) LUL Lu Ul- CD 0 LU OD (D qt 6 0 OD (D I* N -00 0 0 0...2. The quantity multiplying Tk in (40) is called the Onoe funcion : 46 G (M) = +2k2/D. is plotted versus 0 for various k values and for M = 1, 3, and
Mo, Qingkai; Zhang, Tao; Yan, Yining
2016-10-01
There are contradictions among speediness, anti-disturbance performance, and steady-state accuracy caused by traditional PID controller in the existing light source systems of thermal frequency stabilizing laser with double longitudinal modes. In this paper, a new kind of fuzzy adaptive PID controller was designed by combining fuzzy PID control technology and expert system to make frequency stabilizing system obtain the optimal performance. The experiments show that the frequency stability of the designed PID controller is similar to the existing PID controller (the magnitude of frequency stability is less than 10-9 in constant temperature and 10-7 in open air). But the preheating time is shortened obviously (from 10 minutes to 5 minutes) and the anti-disturbance capability is improved significantly (the recovery time needed after strong interference is reduced from 1 minute to 10 seconds).
Influence of left-handed material on the resonant frequency of resonant cavity%左手介质对谐振腔谐振频率的影响∗
Institute of Scientific and Technical Information of China (English)
李培; 王辅忠; 张丽珠; 张光璐
2015-01-01
The quality factor and the resonant frequency of a resonant cavity are the key factors that need to be considered in the process of resonator design. The wall of cavity is composed of conductor materials which are effective tools to generate high-frequency oscillation. The microwave cavity is widely used. From the perspective of the circuit, it has almost all the properties of LC resonance unit, such as mode selection. Therefore, it is widely used in filters, matching circuits, and antenna design. In industrial applications, the demand for high-frequency resonant cavity is relatively large. A traditional method can increase the resonant frequency of the resonant cavity by reducing the size of the cavity or using the high-order modes. However, as both approaches have their limitations, the design results are not ideal. By combining theoretical calculation and simulation, the factors that affect the resonant frequency of the resonator are analyzed. The results show the relationship between material properties of the filling medium and the resonant frequency of the cavity. Theoretical calculations show that when the left-handed materials are used as filling materials in the cavity, the resonant frequency can be increased without changing the size of the cavity. The results of high frequency structure simulator also prove the above result. Therefore, the resonant frequency of the resonator cannot be limited by the cavity size. It can be seen from the data that compared with reducing the size of the resonator or using high-order modes, filling left-handed materials can improve resonant frequency to a greater extent. The obtained conclusion shows a further progress compared with the traditional theory and provides a theoretical basis for the exploration and design of novel resonators.
Coarse-fine adaptive tuned vibration absorber with high frequency resolution
Wang, Xi; Yang, Bintang; You, Jiaxin; Gao, Zhe
2016-11-01
The speed fluctuation of satellite-rotary-mechanisms causes vibration of slightly different frequencies. The critical requirements of satellites need a vibration control device with high frequency resolution to suppress the vibration. This paper presents a coarse-fine adaptive tuned vibration absorber (ATVA) with high frequency resolution. The coarse-fine ATVA which simultaneously satisfies the requirements of high resolution and relatively wide effective bandwidth is capable of tracking the variable exciting frequency adaptively to suppress the vibration of the primary system. The coarse-fine ATVA is divided into a coarse tuning segment and a fine tuning segment. The coarse tuning segment is used to tune the required natural frequency in a relatively wide effective bandwidth and the fine tuning segment can achieve precise tune in a tiny-scale bandwidth. The mathematical model of the coarse tuning and the fine tuning is proposed to design the parameters of the coarse-fine ATVA. The experimental test results indicate the coarse tuning bandwidth of the coarse-fine ATVA is 8.7 Hz to 29 Hz and the minimum resolution of the fine tuning is 0.05 Hz. Moreover, a significant vibration attenuation of 15dB is verified in the effective bandwidth.
Mrňa, L.; Šarbort, M.; Řeřucha, Š.; Jedlička, P.
This paper presents a novel method for optimization and feedback control of laser welding process. It is based on frequency analysis of the light emitted during the process and adaptive shaping of the laser beam achieved by an active optical element. Experimentally observed correlations between the focal properties of the laser beam, the weld depth and the frequency characteristics of the light emissions, which form the basis of the method, are discussed in detail. The functionality and the high efficiency of the method are demonstrated for a variety of welding parameters settings usually used in industrial practice.
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.
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.
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
This paper presents an adaptive wide-area damping controller (WADC) based on generalized predictive control (GPC) and model identification for damping the inter-area low frequency oscillations in large-scale inter-connected power system. A recursive least-squares algorithm (RLSA) with a varying...... forgetting factor is applied to identify online the reduced-order linearlized model which contains dominant inter-area low frequency oscillations. Based on this linearlized model, the generalized predictive control scheme considering control output constraints is employed to obtain the optimal control signal...... 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...
Hein, Annette; Larsen, Jakob Juul; Parsekian, Andrew D.
2017-02-01
Surface nuclear magnetic resonance (NMR) is a unique geophysical method due to its direct sensitivity to water. A key limitation to overcome is the difficulty of making surface NMR measurements in environments with anthropogenic electromagnetic noise, particularly constant frequency sources such as powerlines. Here we present a method of removing harmonic noise by utilizing frequency domain symmetry of surface NMR signals to reconstruct portions of the spectrum corrupted by frequency-domain noise peaks. This method supplements the existing NMR processing workflow and is applicable after despiking, coherent noise cancellation, and stacking. The symmetry based correction is simple, grounded in mathematical theory describing NMR signals, does not introduce errors into the data set, and requires no prior knowledge about the harmonics. Modelling and field examples show that symmetry based noise removal reduces the effects of harmonics. In one modelling example, symmetry based noise removal improved signal-to-noise ratio in the data by 10 per cent. This improvement had noticeable effects on inversion parameters including water content and the decay constant T2*. Within water content profiles, aquifer boundaries and water content are more accurate after harmonics are removed. Fewer spurious water content spikes appear within aquifers, which is especially useful for resolving multilayered structures. Within T2* profiles, estimates are more accurate after harmonics are removed, especially in the lower half of profiles.
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.
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.
Adaptive eigenspace method for inverse scattering problems in the frequency domain
Grote, Marcus J.; Kray, Marie; Nahum, Uri
2017-02-01
A nonlinear optimization method is proposed for the solution of inverse scattering problems in the frequency domain, when the scattered field is governed by the Helmholtz equation. The time-harmonic inverse medium problem is formulated as a PDE-constrained optimization problem and solved by an inexact truncated Newton-type iteration. Instead of a grid-based discrete representation, the unknown wave speed is projected to a particular finite-dimensional basis of eigenfunctions, which is iteratively adapted during the optimization. Truncating the adaptive eigenspace (AE) basis at a (small and slowly increasing) finite number of eigenfunctions effectively introduces regularization into the inversion and thus avoids the need for standard Tikhonov-type regularization. Both analytical and numerical evidence underpins the accuracy of the AE representation. Numerical experiments demonstrate the efficiency and robustness to missing or noisy data of the resulting adaptive eigenspace inversion method.
Ermentrout, B; Pascal, M; Gutkin, B
2001-06-01
There are several different biophysical mechanisms for spike frequency adaptation observed in recordings from cortical neurons. The two most commonly used in modeling studies are a calcium-dependent potassium current I(ahp) and a slow voltage-dependent potassium current, I(m). We show that both of these have strong effects on the synchronization properties of excitatorily coupled neurons. Furthermore, we show that the reasons for these effects are different. We show through an analysis of some standard models, that the M-current adaptation alters the mechanism for repetitive firing, while the afterhyperpolarization adaptation works via shunting the incoming synapses. This latter mechanism applies with a network that has recurrent inhibition. The shunting behavior is captured in a simple two-variable reduced model that arises near certain types of bifurcations. A one-dimensional map is derived from the simplified model.
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.
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.
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.
Thalmayr, Florian; Hashimoto, Ken-Ya; Omori, Tatsuya; Yamaguchi, Masatsune
2010-07-01
This paper demonstrates a novel frequency domain analysis (FDA) to evaluate the scattering behavior of a waveguide mode at arbitrary scattering geometries by a time harmonic simulation based on the finite element method (FEM). To this end, we add an injection-damping mechanism (IDM) to avoid interference at the acoustic input port. The IDM can be easily constructed by a numerical operation. Our approach offers improved time consumption and calculation power necessary over the established method in the time domain. After checking the validity of the proposed method, we discuss the importance of considering wave scattering phenomena in film bulk acoustic wave resonator (FBAR) devices by applying the proposed method to two simplified models of an FBAR device.
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.
Analysis and Comparison of High Frequency Resonance in Small and Large Scale DFIG System
DEFF Research Database (Denmark)
Song, Yipeng; Blaabjerg, Frede; Wang, Xiongfei
2016-01-01
When connected to a parallel compensated weak grid network, both the small and large power scale Doubly Fed Induction Generator (DFIG) system may suffer high frequency resonance (HFR) due to the impedance interaction between the DFIG system and the parallel compensated weak network. Since...... the parameters of the small and large scale DFIG systems, including DFIG machine parameters and the LCL filter parameters, may vary between 10 to 100 times, the impedance modeling results of small and large scale DFIG system are quite different. Based on the built impedance modeling results, the HFR in small...... and large scale DFIG system are theoretically analyzed and compared in this paper with the discussion on the influence of PI controller proportional parameters and the digital control delay on the DFIG system impedance shaping. The experimental validation of small scale DFIG system and the simulation...
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.
Ultralow frequency acoustic resonances and its potential for mitigating tsunami wave formation
Estrada, Hector
2012-01-01
Bubbles display astonishing acoustical properties since they are able to absorb and scatter large amounts of energy coming from waves whose wavelengths are two orders of magnitude larger than the bubble size. Thus, as the interaction distance between bubbles is much larger than the bubble size, clouds of bubbles exhibit collective oscillations which can scatter acoustic waves three orders magnitude larger than the bubble size. Here we propose bubble based systems which resonate at frequencies that match the time scale relevant for seismogenic tsunami wave generation and may mitigate the devastating effects of tsunami waves. Based on a linear approximation, our na\\"ive proposal may open new research paths towards the mitigation of tsunami waves generation.
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.
Akiel, R D; Stepanov, V; Takahashi, S
2016-06-21
Nanodiamond (ND) is an attractive class of nanomaterial for fluorescent labeling, magnetic sensing of biological molecules, and targeted drug delivery. Many of those applications require tethering of target biological molecules on the ND surface. Even though many approaches have been developed to attach macromolecules to the ND surface, it remains challenging to characterize dynamics of tethered molecule. Here, we show high-frequency electron paramagnetic resonance (HF EPR) spectroscopy of nitroxide-functionalized NDs. Nitroxide radical is a commonly used spin label to investigate dynamics of biological molecules. In the investigation, we developed a sample holder to overcome water absorption of HF microwave. Then, we demonstrated HF EPR spectroscopy of nitroxide-functionalized NDs in aqueous solution and showed clear spectral distinction of ND and nitroxide EPR signals. Moreover, through EPR spectral analysis, we investigate dynamics of nitroxide radicals on the ND surface. The demonstration sheds light on the use of HF EPR spectroscopy to investigate biological molecule-functionalized nanoparticles.
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.
Performance of a low-frequency, multi-resonant broadband Tonpilz transducer
Rajapan, Dhilsha
2002-04-01
The underwater performance of a high-power multi-resonant Tonpilz transducer with a nearly flat frequency response and a power handling capability of 2 kW (peak) is reported here. A maximum transmitting voltage response (TVR) value of 156 dB re: 1 μPa/V at 1 m has been achieved at 3 kHz with a specially designed matching coil. A maximum receiving sensitivity (RS) of -164 dB re: 1 V/μPa at 3 kHz has been measured without using a matching coil. The horizontal half-power beam width of the transducer at 4 kHz is 101 degrees with a directivity index of 4 dB. This transmitter can be used for oceanographic applications such as subbottom profiling as well as long-range underwater communication.
Barkat, Ouarda; Benghalia, Abdelmadjid
2009-10-01
In this work, the full-wave method is used for computing the resonant frequency, the bandwidth, and radiation pattern of High temperature superconductor, or an imperfectly conducting annular ring microstrip, which is printed on uniaxial anisotropic substrate. Galerkin’s method is used in the resolution of the electric field integral equation. The TM set of modes issued from the cavity model theory are used to expand the unknown currents on the patch. Numerical results concerning the effect of the anisotropic substrates on the antenna performance are presented and discussed. It is found that microstrip superconducting could give high efficiency with high gain in millimeter wavelengths. Results are compared with previously published data and are found to be in good agreement.
Alves-Pereira, A R; Martinho, J M G; Berberan-Santos, M N
2007-01-01
The relation between the jump length probability distribution function and the spectral line profile in resonance atomic radiation trapping is considered for Partial Frequency Redistribution (PFR) between absorbed and reemitted radiation. The single line Opacity Distribution Function [M.N. Berberan-Santos et.al. J.Chem.Phys. 125, 174308 (2006)] is generalized for PFR and used to discuss several possible redistribution mechanisms (pure Doppler broadening, combined natural and Doppler broadening and combined Doppler, natural and collisional broadening). It is shown that there are two coexisting scales with a different behavior: the small scale is controlled by the intricate PFR details while the large scale is essentially given by the atom rest frame redistribution asymptotic. The pure Doppler and combined natural, Doppler and collisional broadening are characterized by both small and large scale superdiffusive Levy flight behaviors while the combined natural and Doppler case has an anomalous small scale behavi...
Photonic Weyl point in a two-dimensional resonator lattice with a synthetic frequency dimension
Lin, Qian; Xiao, Meng; Yuan, Luqi; Fan, Shanhui
2016-12-01
Weyl points, as a signature of 3D topological states, have been extensively studied in condensed matter systems. Recently, the physics of Weyl points has also been explored in electromagnetic structures such as photonic crystals and metamaterials. These structures typically have complex three-dimensional geometries, which limits the potential for exploring Weyl point physics in on-chip integrated systems. Here we show that Weyl point physics emerges in a system of two-dimensional arrays of resonators undergoing dynamic modulation of refractive index. In addition, the phase of modulation can be controlled to explore Weyl points under different symmetries. Furthermore, unlike static structures, in this system the non-trivial topology of the Weyl point manifests in terms of surface state arcs in the synthetic space that exhibit one-way frequency conversion. Our system therefore provides a versatile platform to explore and exploit Weyl point physics on chip.
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.
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.
Le, Kelvin; Li, Xiaosong; Figueroa, Daniel; Towner, Rheal A.; Garteiser, Philippe; Saunders, Debra; Smith, Nataliya; Liu, Hong; Hode, Tomas; Nordquist, Robert E.; Chen, Wei R.
2011-12-01
Laser immunotherapy (LIT) uses a synergistic approach to treat cancer systemically through local laser irradiation and immunological stimulation. Currently, LIT utilizes dye-assisted noninvasive laser irradiation to achieve selective photothermal interaction. However, LIT faces difficulties treating deeper tumors or tumors with heavily pigmented overlying skin. To circumvent these barriers, we use interstitial laser irradiation to induce the desired photothermal effects. The purpose of this study is to analyze the thermal effects of interstitial irradiation using proton resonance frequency (PRF). An 805-nm near-infrared laser with an interstitial cylindrical diffuser was used to treat rat mammary tumors. Different power settings (1.0, 1.25, and 1.5 W) were applied with an irradiation duration of 10 min. The temperature distributions of the treated tumors were measured by a 7 T magnetic resonance imager using PRF. We found that temperature distributions in tissue depended on both laser power and time settings, and that variance in tissue composition has a major influence in temperature elevation. The temperature elevations measured during interstitial laser irradiation by PRF and thermocouple were consistent, with some variations due to tissue composition and the positioning of the thermocouple's needle probes. Our results indicated that, for a tissue irradiation of 10 min, the elevation of rat tumor temperature ranged from 8 to 11°C for 1 W and 8 to 15°C for 1.5 W. This is the first time a 7 T magnetic resonance imager has been used to monitor interstitial laser irradiation via PRF. Our work provides a basic understanding of the photothermal interaction needed to control the thermal damage inside a tumor using interstitial laser treatment. Our work may lead to an optimal protocol for future cancer treatment using interstitial phototherapy in conjunction with immunotherapy.
Energy Technology Data Exchange (ETDEWEB)
Grafe, H.J.; Vyalikh, A.; Vavilova, J.; Buchner, B. [IFW Dresden, Institute for Solid State Research, Dresden (Germany); Curro, N.J. [Department of Physics, University of California, Davis, CA (United States); Young, B.L. [Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan (China); Gu, G.D.; Hucker, M. [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY (United States); Vavilova, J. [Kazan Zavoiskiy Physical-Technical Institute, Kazan (Russian Federation)
2010-10-15
We report detailed {sup 17}O, {sup 139}La, and {sup 63,65}Cu Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) measurements in a stripe ordered La{sub 1.875}Ba{sub 0.125}CuO{sub 4} single crystal and in oriented powder samples of La{sub 1.8-x}Eu{sub 0.2}Sr{sub x}CuO{sub 4}. We observe a partial wipe out of the {sup 17}O NMR intensity and a simultaneous drop of the {sup 17}O electric field gradient (EFG) at low temperatures where the spin stripe order sets in. In contrast, the {sup 63,65}Cu intensity is completely wiped out at the same temperature. The drop of the {sup 17}O quadrupole frequency is compatible with a charge stripe order. The {sup 17}O spin lattice relaxation rate shows a peak similar to that of the {sup 139}La, which is of magnetic origin. This peak is doping dependent and is maximal at x {approx} 1/8. (authors)
Maity, Arnab; Hocht, Leonhard; Heise, Christian; Holzapfel, Florian
2016-11-28
A new efficient adaptive optimal control approach is presented in this paper based on the indirect model reference adaptive control (MRAC) architecture for improvement of adaptation and tracking performance of the uncertain system. The system accounts here for both matched and unmatched unknown uncertainties that can act as plant as well as input effectiveness failures or damages. For adaptation of the unknown parameters of these uncertainties, the frequency selective learning approach is used. Its idea is to compute a filtered expression of the system uncertainty using multiple filters based on online instantaneous information, which is used for augmentation of the update law. It is capable of adjusting a sudden change in system dynamics without depending on high adaptation gains and can satisfy exponential parameter error convergence under certain conditions in the presence of structured matched and unmatched uncertainties as well. Additionally, the controller of the MRAC system is designed using a new optimal control method. This method is a new linear quadratic regulator-based optimal control formulation for both output regulation and command tracking problems. It provides a closed-form control solution. The proposed overall approach is applied in a control of lateral dynamics of an unmanned aircraft problem to show its effectiveness.
Frequency-Domain Adaptive Algorithm for Network Echo Cancellation in VoIP
Directory of Open Access Journals (Sweden)
Patrick A. Naylor
2008-05-01
Full Text Available We propose a new low complexity, low delay, and fast converging frequency-domain adaptive algorithm for network echo cancellation in VoIP exploiting MMax and sparse partial (SP tap-selection criteria in the frequency domain. We incorporate these tap-selection techniques into the multidelay filtering (MDF algorithm in order to mitigate the delay inherent in frequency-domain algorithms. We illustrate two such approaches and discuss their tradeoff between convergence performance and computational complexity. Simulation results show an improvement in convergence rate for the proposed algorithm over MDF and significantly reduced complexity. The proposed algorithm achieves a convergence performance close to that of the recently proposed, but substantially more complex improved proportionate MDF (IPMDF algorithm.
Hand movements classification for myoelectric control system using adaptive resonance theory.
Jahani Fariman, H; Ahmad, Siti A; Hamiruce Marhaban, M; Alijan Ghasab, M; Chappell, Paul H
2016-03-01
This research proposes an exploratory study of a simple, accurate, and computationally efficient movement classification technique for prosthetic hand application. Surface myoelectric signals were acquired from the four muscles, namely, flexor carpi ulnaris, extensor carpi radialis, biceps brachii, and triceps brachii, of four normal-limb subjects. The signals were segmented, and the features were extracted with a new combined time-domain feature extraction method. Fuzzy C-means clustering method and scatter plot were used to evaluate the performance of the proposed multi-feature versus Hudgins' multi-feature. The movements were classified with a hybrid Adaptive Resonance Theory-based neural network. Comparative results indicate that the proposed hybrid classifier not only has good classification accuracy (89.09%) but also a significantly improved computation time.
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.
Loures, Cristian Redondo; Biancalana, Fabio
2015-01-01
Starting from the infinite-dimensional Ikeda map, we derive an extended temporal Lugiato-Lefever equation that may account for the effects of the conjugate electromagnetic fields (also called `negative frequency fields'). In the presence of nonlinearity in a ring cavity, these fields lead to new forms of modulational instability and resonant radiations. Numerical simulations based on the new extended Lugiato-Lefever model show that the negative-frequency resonant radiations emitted by ultrashort cavity solitons can impact Kerr frequency comb formation in externally pumped temporal optical cavities of small size. Our theory is very general, is not based on the slowly-varying envelope approximation, and the predictions are relevant to all kinds of resonators, such as fiber loops, microrings and microtoroids.
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.
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.
Grossberg, Stephen
2013-01-01
Adaptive Resonance Theory, or ART, is a cognitive and neural theory of how the brain autonomously learns to categorize, recognize, and predict objects and events in a changing world. This article reviews classical and recent developments of ART, and provides a synthesis of concepts, principles, mechanisms, architectures, and the interdisciplinary data bases that they have helped to explain and predict. The review illustrates that ART is currently the most highly developed cognitive and neural theory available, with the broadest explanatory and predictive range. Central to ART's predictive power is its ability to carry out fast, incremental, and stable unsupervised and supervised learning in response to a changing world. ART specifies mechanistic links between processes of consciousness, learning, expectation, attention, resonance, and synchrony during both unsupervised and supervised learning. ART provides functional and mechanistic explanations of such diverse topics as laminar cortical circuitry; invariant object and scenic gist learning and recognition; prototype, surface, and boundary attention; gamma and beta oscillations; learning of entorhinal grid cells and hippocampal place cells; computation of homologous spatial and temporal mechanisms in the entorhinal-hippocampal system; vigilance breakdowns during autism and medial temporal amnesia; cognitive-emotional interactions that focus attention on valued objects in an adaptively timed way; item-order-rank working memories and learned list chunks for the planning and control of sequences of linguistic, spatial, and motor information; conscious speech percepts that are influenced by future context; auditory streaming in noise during source segregation; and speaker normalization. Brain regions that are functionally described include visual and auditory neocortex; specific and nonspecific thalamic nuclei; inferotemporal, parietal, prefrontal, entorhinal, hippocampal, parahippocampal, perirhinal, and motor cortices
Zhang, Shuangxi; Kishimoto, Yasuaki
2016-01-01
This paper studies about circular polarized high frequency wave driving charged particle in strong magnetic field, and a new gyro resonant Lie perturbed transformation theory is given by adding a new total differential term to the original first order 1-form to remove the secularity of relevant infinitesimal generators. The time consumption of numerical simulation based on this resonant theory has an advantage over real orbit simulation if the magnetic field has almost a constant amplitude in the simulation spatial region, while the advantage disappears when the amplitude changes obviously in the simulation spatial region. A simple numerical experiment is given to test the new resonant theory and its time consumption property.
2008-07-25
report results for a single-frequency SF resonantly cladding-pumped Yb-free large mode area LMA erbium-doped fiber amplifier EDFA with nearly 50...original demonstration of a SF resonantly cladding-pumped LMA EDFA . We obtained a diffraction-limited SF output of 9.3 W, which is also a record power...output obtained for resonantly cladding-pumped LMA EDFA . © 2008 American Institute of Physics. DOI: 10.1063/1.2964189 Recent advances in eye-safe 1.5
Hanna, Noel; Smith, John; Wolfe, Joe
2016-05-01
The frequencies, magnitudes, and bandwidths of vocal tract resonances are all important in understanding and synthesizing speech. High precision acoustic impedance spectra of the vocal tracts of 10 subjects were measured from 10 Hz to 4.2 kHz by injecting a broadband acoustic signal through the lips. Between 300 Hz and 4 kHz the acoustic resonances R (impedance minima measured through the lips) and anti-resonances R¯ (impedance maxima) associated with the first three voice formants, have bandwidths of ∼50 to 90 Hz for men and ∼70 to 90 Hz for women. These acoustic resonances approximate those of a smooth, dry, rigid cylinder of similar dimensions, except that their bandwidths indicate higher losses in the vocal tract. The lossy, inertive load and airflow caused by opening the glottis further increase the bandwidths observed during phonation. The vocal tract walls are not rigid and measurements show an acousto-mechanical resonance R0 ∼ 20 Hz and anti-resonance R¯0∼200 Hz. These give an estimate of wall inertance consistent with an effective thickness of 1-2 cm and a wall stiffness of 2-4 kN m(-1). The non-rigidity of the tract imposes a lower limit of the frequency of the first acoustic resonance fR1 and the first formant F1.
Velceanu, C. I.
1974-01-01
An experimental setup is reported that permits very accurate measurements of the resonance frequencies of long cylindrical beams fixed in the middle and whose size can vary within wide limits. It also permits measurement of the width of the resonance curve. It is shown that the Poisson effect can be brought to light for relatively long beams and for relatively short beams. Poisson ratio, values obtained with this method argue in favor of using the low frequency region for determining elastic constants of solids.
Babbs, Charles F
2011-01-01
To explore the fundamental biomechanics of sound frequency transduction in the cochlea, a two-dimensional analytical model of the basilar membrane was constructed from first principles. Quantitative analysis showed that axial forces along the membrane are negligible, condensing the problem to a set of ordered one-dimensional models in the radial dimension, for which all parameters can be specified from experimental data. Solutions of the radial models for asymmetrical boundary conditions produce realistic deformation patterns. The resulting second-order differential equations, based on the original concepts of Helmholtz and Guyton, and including viscoelastic restoring forces, predict a frequency map and amplitudes of deflections that are consistent with classical observations. They also predict the effects of an observation hole drilled in the surrounding bone, the effects of curvature of the cochlear spiral, as well as apparent traveling waves under a variety of experimental conditions. A quantitative rendition of the classical Helmholtz-Guyton model captures the essence of cochlear mechanics and unifies the competing resonance and traveling wave theories.
Quantitative Reappraisal of the Helmholtz-Guyton Resonance Theory of Frequency Tuning in the Cochlea
Directory of Open Access Journals (Sweden)
Charles F. Babbs
2011-01-01
Full Text Available To explore the fundamental biomechanics of sound frequency transduction in the cochlea, a two-dimensional analytical model of the basilar membrane was constructed from first principles. Quantitative analysis showed that axial forces along the membrane are negligible, condensing the problem to a set of ordered one-dimensional models in the radial dimension, for which all parameters can be specified from experimental data. Solutions of the radial models for asymmetrical boundary conditions produce realistic deformation patterns. The resulting second-order differential equations, based on the original concepts of Helmholtz and Guyton, and including viscoelastic restoring forces, predict a frequency map and amplitudes of deflections that are consistent with classical observations. They also predict the effects of an observation hole drilled in the surrounding bone, the effects of curvature of the cochlear spiral, as well as apparent traveling waves under a variety of experimental conditions. A quantitative rendition of the classical Helmholtz-Guyton model captures the essence of cochlear mechanics and unifies the competing resonance and traveling wave theories.
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.
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.
Huang, Yulu; Wang, Haipeng; Rimmer, Robert A.; Wang, Shaoheng; Guo, Jiquan
2016-12-01
Quarter wavelength resonator (QWR) based deflecting cavities with the capability of supporting multiple odd-harmonic modes have been developed for an ultrafast periodic kicker system in the proposed Jefferson Lab Electron Ion Collider (JLEIC, formerly MEIC). Previous work on the kicking pulse synthesis and the transverse beam dynamics tracking simulations show that a flat-top kicking pulse can be generated with minimal emittance growth during injection and circulation of the cooling electron bunches. This flat-top kicking pulse can be obtained when a DC component and 10 harmonic modes with appropriate amplitude and phase are combined together. To support 10 such harmonic modes, four QWR cavities are used with 5, 3, 1, and 1 modes, respectively. In the multiple-mode cavities, several slightly tapered segments of the inner conductor are introduced to tune the higher order deflecting modes to be harmonic, and stub tuners are used to fine tune each frequency to compensate for potential errors. In this paper, we summarize the electromagnetic design of the five-mode cavity, including the geometry optimization to get high transverse shunt impedance, the frequency tuning and sensitivity analysis, and the single loop coupler design for coupling to all of the harmonic modes. In particular we report on the design and fabrication of a half-scale copper prototype of this proof-of-principle five-odd-mode cavity, as well as the rf bench measurements. Finally, we demonstrate mode superposition in this cavity experimentally, which illustrates the kicking pulse generation concept.
Patch Antenna based on a Photovoltaic Cell with a Dual resonance Frequency
Directory of Open Access Journals (Sweden)
C. Baccouch
2016-11-01
Full Text Available The present work was to use photovoltaic solar cells in patch antenna structures. The radiating patch element of a patch antenna was replaced by a solar cell. Direct Current (DC generation remained the original feature of the solar cell, but additionally it was now able to receive and transmit electromagnetic waves. Here, we used a new patch antenna structure based on a photovoltaic solar cell. It was then used to collect photo-generated current as well as Radio Frequency (RF transmission. A mathematical model which would serve the minimization of power losses of the cell and therefore the improvement in the conversion efficiency was studied. A simulation allowed analysing the performance of the antenna, with a silicon material, and testing its parameters such as the reflection coefficient (S11, gain, directivity and radiated power. The performance analysis of the solar cell patch antenna was conducted using Advanced Design System (ADS software. Simulation results for this antenna showed a dual resonance frequency of 5.77 GHz and of 6.18 GHz with an effective return loss of -38.22dB and a gain of 1.59dBi.
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.
Monaco, Simona; Cavina-Pratesi, Cristiana; Sedda, Anna; Fattori, Patrizia; Galletti, Claudio; Culham, Jody C
2011-11-01
Reach-to-grasp actions require coordination of different segments of the upper limbs. Previous studies have examined the neural substrates of arm transport and hand grip components of such actions; however, a third component has been largely neglected: the orientation of the wrist and hand appropriately for the object. Here we used functional magnetic resonance imaging adaptation (fMRA) to investigate human brain areas involved in processing hand orientation during grasping movements. Participants used the dominant right hand to grasp a rod with the four fingers opposing the thumb or to reach and touch the rod with the knuckles without visual feedback. In a control condition, participants passively viewed the rod. Trials in a slow event-related design consisted of two sequential stimuli in which the rod orientation changed (requiring a change in wrist posture while grasping but not reaching or looking) or remained the same. We found reduced activation, that is, adaptation, in superior parieto-occipital cortex (SPOC) when the object was repeatedly grasped with the same orientation. In contrast, there was no adaptation when reaching or looking at an object in the same orientation, suggesting that hand orientation, rather than object orientation, was the critical factor. These results agree with recent neurophysiological research showing that a parieto-occipital area of macaque (V6A) is modulated by hand orientation during reach-to-grasp movements. We suggest that the human dorsomedial stream, like that in the macaque, plays a key role in processing hand orientation in reach-to-grasp movements.
Ekaterina I. Radeva; Esmeryan, Karekin D.; Avramov, Ivan D.
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 ...
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.
Nakagawa, Seiji
2011-04-01
Mechanical properties (seismic velocities and attenuation) of geological materials are often frequency dependent, which necessitates measurements of the properties at frequencies relevant to a problem at hand. Conventional acoustic resonant bar tests allow measuring seismic properties of rocks and sediments at sonic frequencies (several kilohertz) that are close to the frequencies employed for geophysical exploration of oil and gas resources. However, the tests require a long, slender sample, which is often difficult to obtain from the deep subsurface or from weak and fractured geological formations. In this paper, an alternative measurement technique to conventional resonant bar tests is presented. This technique uses only a small, jacketed rock or sediment core sample mediating a pair of long, metal extension bars with attached seismic source and receiver—the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the length and mass added to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The experiment can be conducted under elevated confining pressures up to tens of MPa and temperatures above 100 °C, and concurrently with x-ray CT imaging. The described split Hopkinson resonant bar test is applied in two steps. First, extension and torsion-mode resonance frequencies and attenuation of the entire system are measured. Next, numerical inversions for the complex Young's and shear moduli of the sample are performed. One particularly important step is the correction of the inverted Young's moduli for the effect of sample-rod interfaces. Examples of the application are given for homogeneous, isotropic polymer samples, and a natural rock sample.
Energy Technology Data Exchange (ETDEWEB)
Nakagawa, S.
2011-04-01
Mechanical properties (seismic velocities and attenuation) of geological materials are often frequency dependent, which necessitates measurements of the properties at frequencies relevant to a problem at hand. Conventional acoustic resonant bar tests allow measuring seismic properties of rocks and sediments at sonic frequencies (several kilohertz) that are close to the frequencies employed for geophysical exploration of oil and gas resources. However, the tests require a long, slender sample, which is often difficult to obtain from the deep subsurface or from weak and fractured geological formations. In this paper, an alternative measurement technique to conventional resonant bar tests is presented. This technique uses only a small, jacketed rock or sediment core sample mediating a pair of long, metal extension bars with attached seismic source and receiver - the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the length and mass added to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The experiment can be conducted under elevated confining pressures up to tens of MPa and temperatures above 100 C, and concurrently with x-ray CT imaging. The described Split Hopkinson Resonant Bar (SHRB) test is applied in two steps. First, extension and torsion-mode resonance frequencies and attenuation of the entire system are measured. Next, numerical inversions for the complex Young's and shear moduli of the sample are performed. One particularly important step is the correction of the inverted Young's moduli for the effect of sample-rod interfaces. Examples of the application are given for homogeneous, isotropic polymer samples and a natural rock sample.
Seliger, J; Zagar, V
2009-08-01
The possibilities of dynamically polarizing proton spin system via the quadrupole (14)N spin system in low magnetic field are analyzed. The increase of the proton magnetization is calculated. The polarization rate of the proton spin system is related to the transition probabilities per unit time between the (14)N quadrupole energy levels and proton energy levels. The experiments performed in 1,3,5-triazine confirm the results of the theoretical analysis. A new double resonance technique is proposed for the measurement of nuclear quadrupole resonance frequencies nu(Q) of the order of 100kHz and lower. The technique is based on magnetic field cycling between a high and a low static magnetic field and observation of the proton NMR signal in the high magnetic field. In the low magnetic field the quadrupole nuclei and protons resonantly interact at the proton Larmor frequency nu(H)=nu(Q)/2. The quadrupole nuclei are simultaneously excited by a resonant rf magnetic field oriented along the direction of the low static magnetic field. The experimental procedure is described and the sensitivity of the new technique is estimated. Some examples of the measurement of low (14)N and (2)H nuclear quadrupole resonance frequencies are presented.
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.
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...
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
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.
Wang, Yuanwu; Zhang, Minming; Lu, Luluzi; Li, Meifeng; Wang, Jinghao; Zhou, Feiya; Dai, Jing; Deng, Lei; Liu, Deming
2016-01-01
In this paper, a novel double-slot microring resonator is proposed to produce flat dispersion of 0-3.8 ps/(nm km) over 1150 nm wavelength range. Moreover, the dispersion tailoring with different structural parameters of the proposed microring resonator is analyzed and simulated. The simulation results show that the dispersion fluctuation can be tailored by the height of the central and bottom As2S3 layer, and the slope can be adjusted by the waveguide width and lower SiO2 slot thickness. Furthermore, by means of the Lugiato-Lefever equation, an ultra-flat and broad optical frequency comb with 7-dB bandwidth of 1155 nm (1855-3010 nm) is obtained based on such dispersion-optimized resonator. The proposed double-slot microring resonator shows potential application in both telecommunication and mid-infrared research domain.
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).
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.
Hartmann, Mitra J.; Johnson, Nicholas J.; Towal, R. Blythe; Assad, Christopher
2003-01-01
We investigated the natural resonance properties and damping characteristics of rat macrovibrissae (whiskers). Isolated whiskers rigidly fixed at the base showed first-mode resonance peaks between 27 and 260 Hz, principally depending on whisker length. These experimentally measured resonant frequencies were matched using a theoretical model of the whisker as a conical cantilever beam, with Young's modulus as the only free parameter. The best estimate for Young's modulus was approximately 3-4 GPa. Results of both vibration and impulse experiments showed that the whiskers are strongly damped, with damping ratios between 0.11 and 0.17. In the behaving animal, whiskers that deflected past an object were observed to resonate but were damped significantly more than isolated whiskers. The time course of damping varied depending on the individual whisker and the phase of the whisking cycle, which suggests that the rat may modulate biomechanical parameters that affect damping. No resonances were observed for whiskers that did not contact the object or during free whisking in air. Finally, whiskers on the same side of the face were sometimes observed to move in opposite directions over the full duration of a whisk. We discuss the potential roles of resonance during natural exploratory behavior and specifically suggest that resonant oscillations may be important in the rat's tactile detection of object boundaries.
Directory of Open Access Journals (Sweden)
Rokhsareh Sadeghi
2016-05-01
Full Text Available Objectives: Implant primary stability is one of the important factors in achieving implant success. The osteotome technique may improve primary stability in patients with poor bone quality. The aim of this study was to compare implant stability using two different techniques namely osteotome versus conventional drilling in the posterior maxilla.Materials and Methods: In this controlled randomized clinical trial, 54 dental implants were placed in 32 patients; 29 implants were placed in the osteotome group and 25 in the conventional drilling group. Implant stability was assessed at four time intervals namely at baseline, one, two and three months after implant placement using resonance frequency analysis (RFA.Results: Primary stability based on implant stability quotient (ISQ units was 71.4±7 for the osteotome group and 67.4±10 for the control group. There was no statistically significant difference between the two groups in implant stability at any of the measurement times. In each group, changes in implant stability from baseline to one month and also from two months to three months post-operatively were not significant but from one month to two months after implant placement, implant stability showed a significant increase in both groups. Conclusion: The results of this study revealed that in both techniques, good implant stability was achieved and osteotome technique did not have any advantage compared to conventional drilling in this regard.
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.
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.
Cho, Franklin; Takahashi, Susumu
2014-03-01
Nano-sized diamond or nanodiamond is a fascinating material for potential applications of fluorescence imaging and magnetic sensing of biological systems via nitrogen-vacancy defect centers in diamonds. Sensitivity of the magnetic sensing strongly depends on coupling to surrounding environmental noises, thus understanding of the environment is critical to realize the application. In the present study, we employ multi-frequency (X-band, 115 GHz and 230 GHz) continuous-wave (cw) and pulsed electron spin resonance (ESR) spectroscopy to investigate impurity contents and spin relaxation properties in various sizes of nanodiamonds. Spectra taken with our home-built 230/115 GHz cw/pulsed ESR spectrometer shows presence of two major impurity contents; single substitutional nitrogen impurities (P1) also common in bulk diamonds and paramagnetic impurities (denoted as X) unique to nanodiamonds. The ESR measurement also shows a strong dependence of the population ratio between P1 and X on particle size. Furthermore, we will discuss the nature of spin-lattice relaxation time T1 of nanodiamonds studied by pulsed ESR measurements at X-band, 115 GHz and 230 GHz.
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.
Shokri, Mehran; Daraeighadikolaei, Arash
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 and 1, 2, 3, 4, 5, 7, and 11 weeks after the implant surgery. Results. Among fifteen implants, the lowest mean stability measurement was for the 4th week after surgery in all bone types. At placement, the mean ISQ obtained with the magnetic device was 77.2 with 95% confidence interval (CI) = 2.49, and then it decreased until the 4th week to 72.13 (95% CI = 2.88), and at the last measurement, the mean implant stability significantly (P value implant placement. These suggestions need to be further assessed through future studies. PMID:23737790
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.
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%
Linear systems modeling of adaptive optics in the spatial-frequency domain.
Ellerbroek, Brent L
2005-02-01
Spatial-frequency domain techniques have traditionally been applied to obtain estimates for the independent effects of a variety of individual error sources in adaptive optics (AO). Overall system performance is sometimes estimated by introducing the approximation that these individual error terms are statistically independent, so that their magnitudes may be summed in quadrature. More accurate evaluation methods that account for the correlations between the individual error sources have required Monte Carlo simulations or large matrix calculations that can take much longer to compute, particularly as the order of the AO system increases beyond a few hundred degrees of freedom. We describe an approach to evaluating AO system performance in the spatial-frequency domain that is relatively computationally efficient but still accounts for many of the interactions between the fundamental error sources in AO. We exploit the fact that (in the limits of an infinite aperture and geometrical optics) all the basic wave-front propagation, sensing, and correction processes that describe the behavior of an AO system are spatial-filtering operations in the Fourier domain. Essentially all classical wave-front control algorithms and evaluation formulas are expressed in terms of these filters and may therefore be evaluated one spatial-frequency component at a time. Performance estimates for very-high-order AO systems may be obtained in 1 to 2 orders of magnitude less time than needed when detailed simulations or analytical models in the spatial domain are used, with a relative discrepancy of 5% to 10% for typical sample problems.
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.
Energy Technology Data Exchange (ETDEWEB)
Cho, F. H. [Department of Physics, University of Southern California, Los Angeles, California 90089 (United States); Stepanov, V. [Department of Chemistry, University of Southern California, Los Angeles, California 90089 (United States); Takahashi, S., E-mail: susumu.takahashi@usc.edu [Department of Chemistry, University of Southern California, Los Angeles, California 90089 (United States); Department of Physics, University of Southern California, Los Angeles, California 90089 (United States)
2014-07-15
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 T. 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 {sup 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.
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.
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).
Directory of Open Access Journals (Sweden)
Ekaterina I. Radeva
2012-05-01
Full Text Available 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 a RF-plasma polymerization process, RSAW sensor resonators optimized for maximum gas sensitivity have been coated with chemosensitive HMDSO films at 4 different thicknesses: 50, 100, 150 and 250 nm. Their TFCs have been measured over a (−100 to +110 °C temperature range and compared to the TFC of an uncoated device. An exponential 2,500 ppm downshift of the resonant frequency and a 40 K downshift of the sensor’s turn-over temperature (TOT are observed when the HMDSO thickness increases from 0 to 250 nm. A partial temperature compensation effect caused by the film is also observed. A third order polynomial fit provides excellent agreement with the experimental TFC curve. The frequency downshift due to mass loading by the film, the TOT and the temperature coefficients are unambiguously related to each other.
DEFF Research Database (Denmark)
an impetus or drive to that account: change, innovation, rupture, or discontinuity. Resonances: Historical Essays on Continuity and Change explores the historiographical question of the modes of interrelation between these motifs in historical narratives. The essays in the collection attempt to realize...... theoretical consciousness through historical narrative ‘in practice’, by discussing selected historical topics from Western cultural history, within the disciplines of history, literature, visual arts, musicology, archaeology, philosophy, and theology. The title Resonances indicates the overall perspective...
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
Liu, Zheng; Lin, Zhifang; Chui, S T
2004-01-01
The Mie scattering of electromagnetic waves of wave vector k by spherical negative-refractive-index particles of radius a exhibits an unusual resonance at ka-->0. The scattering enhancement from the ka-->0 resonance is insensitive to the size of scatterers, distinct from the Mie scattering resonances from positive-refractive-index particles. For media consisting of a collection of the negative-refractive-index particles, the unusual resonance results in a significant reduction of the localization parameter, providing a possibility to reach the light localization transition by reducing the wave vector k, in analogy to electronic systems.
Assessing risk of thyroid cancer using resonance-frequency based electrical impedance measurements
Zheng, Bin; Tublin, Mitchell E.; Lederman, Dror; Klym, Amy H.; Brown, Erica D.; Gur, David
2011-03-01
The incidence of thyroid cancer has risen faster than many malignancies and has nearly doubled in the USA over the past 30 years. Palpable nodules and subclinical nodules detected by imaging are found in a large percentage of the USA population. Most of these (.>95%) are fortunately benign. This vast reservoir of nodules makes the detection and diagnosis of thyroid cancer a diagnostic dilemma. Ultrasound guided Fine Needle Aspiration Biopsy (FNAB) is excellent for triaging patients but up to 25% of FNABs are inconclusive. As a result, definitive diagnosis is often only possible with a diagnostic lobectomy; many thousands of these are performed in the USA annually for ultimately benign disease. It would be extremely beneficial if we could develop a non-invasive procedure that could assist the diagnostician in reliably predicting the likelihood of malignancy of otherwise indeterminate thyroid nodules, thereby reducing the number of these "exploratory/diagnostic" lobectomies performed under general anesthesia. Electrical Impedance Spectroscopy (EIS) was considered as a possible approach to address this problem. However, the diagnostic accuracy of EIS is too low for routine clinical use to date. In our group, we developed a substantially modified technology termed Resonance-frequency Electrical Impedance Spectroscopy (REIS), which yields usable information for classifying risk of having breast abnormalities. We preliminarily applied REIS to measure signals on participants having thyroid nodules aiming to assess whether we can assist in improving diagnosis of indeterminate thyroid nodules. In this study we present a new multi-probe based REIS device specifically designed for the assessment of indeterminate thyroid nodules. Our preliminary assessment presented here demonstrates the feasibility of using this proposed REIS device in a busy tertiary care center.
Qiao, Zijian; Lei, Yaguo; Lin, Jing; Jia, Feng
2017-02-01
In mechanical fault diagnosis, most traditional methods for signal processing attempt to suppress or cancel noise imbedded in vibration signals for extracting weak fault characteristics, whereas stochastic resonance (SR), as a potential tool for signal processing, is able to utilize the noise to enhance fault characteristics. The classical bistable SR (CBSR), as one of the most widely used SR methods, however, has the disadvantage of inherent output saturation. The output saturation not only reduces the output signal-to-noise ratio (SNR) but also limits the enhancement capability for fault characteristics. To overcome this shortcoming, a novel method is proposed to extract the fault characteristics, where a piecewise bistable potential model is established. Simulated signals are used to illustrate the effectiveness of the proposed method, and the results show that the method is able to extract weak fault characteristics and has good enhancement performance and anti-noise capability. Finally, the method is applied to fault diagnosis of bearings and planetary gearboxes, respectively. The diagnosis results demonstrate that the proposed method can obtain larger output SNR, higher spectrum peaks at fault characteristic frequencies and therefore larger recognizable degree than the CBSR method.
TonThat, Dinh M.; Clarke, John
1996-08-01
A spectrometer based on a dc superconducting quantum interference device (SQUID) has been developed for the direct detection of nuclear magnetic resonance (NMR) or nuclear quadrupole resonance (NQR) at frequencies up to 5 MHz. The sample is coupled to the input coil of the niobium-based SQUID via a nonresonant superconducting circuit. The flux locked loop involves the direct offset integration technique with additional positive feedback in which the output of the SQUID is coupled directly to a low-noise preamplifier. Precession of the nuclear quadrupole spins is induced by a magnetic field pulse with the feedback circuit disabled; subsequently, flux locked operation is restored and the SQUID amplifies the signal produced by the nuclear free induction signal. The spectrometer has been used to detect 27Al NQR signals in ruby (Al2O3[Cr3+]) at 359 and 714 kHz.
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.
Directory of Open Access Journals (Sweden)
Ahmed Elazab
2015-01-01
Full Text Available 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.
Frequency tuning of single photons from a whispering-gallery mode resonator to MHz-wide transitions
DEFF Research Database (Denmark)
Schunk, G.; Vogl, U.; Sedlmeir, F.
2016-01-01
Quantum repeaters rely on interfacing flying qubits with quantum memories. The most common implementations include a narrowband single photon matched in bandwidth and central frequency to an atomic system. Previously, we demonstrated the compatibility of our versatile source of heralded single...... photons, which is based on parametric down-conversion in a triply resonant whispering-gallery mode resonator, with alkaline transitions [Schunk et al., Optica 2015, 2, 773]. In this paper, we analyse our source in terms of phase matching, available wavelength-tuning mechanisms and applications...... to narrowband atomic systems. We resonantly address the D1 transitions of caesium and rubidium with this optical parametric oscillator pumped above its oscillation threshold. Below threshold, the efficient coupling of single photons to atomic transitions heralded by single telecom-band photons is demonstrated...
Vincent, John J.
The delineation of analysis techniques for high power radio frequency resonators, used as a fundamental component of particle accelerators, receives little attention in the literature. This dissertation reviews, describes, and develops techniques for resolving a transmission line mode rf resonator into an approximate equivalent circuit. Specifically, it presents a toolbox of techniques used to model and represent rf structures. One technique develops models of transmission lines with varying characteristic impedance (referred to as non-uniform) using multiple series connected circuits consisting of lumped elements and constant impedance transmission lines based on a conserved energy approach. This technique is tested for exponentially tapered and linearly tapered quarter-wave resonators. Another technique developed, maps transmission lines with arbitrary cross-sections (referred to as nonstandard) to a standard structure that preserves the characteristic impedance and loss properties of the original line. The techniques developed are applied to the analysis of the complex K1200 Superconducting Cyclotron rf resonators at the National Superconducting Cyclotron Laboratory (NSCL). The results predicted from the model are compared to measurements. The K1200 rf resonators are tunable over the frequency range of 9.5 to 27 MHz with tuning stems that vary from 300 cm to 11 cm respectively. The resonators are operated in the continuos wave (cw) mode and sustain peak voltages of up to 180 kV requiring drive power of up to 250 kW. Using the techniques developed, the resonant frequency versus tuning stem position was predicted to within a positioning error that varied from 1 to 3.5 cm over the tuning range of 9.5 to 27 Mhz. The discrepancy between model predictions and the experimental data for the resonator power dissipation is postulated to be due to high surface resistance in regions where the rf surfaces were heavily worked or welded. After adjusting the surface resistance
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.
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
We investigate the electromagnetic response of asymmetric broadside coupled split-ring resonators (ABC-SRRs) as a function of the relative in-plane displacement between the two component SRRs. The asymmetry is defined as the difference in the capacitive gap widths (Δg) between the two resonators ...
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.
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...
Vieira, H. S.; Bezerra, V. B.
2016-10-01
We apply the confluent Heun functions to study the resonant frequencies (quasispectrum), the Hawking radiation and the scattering process of scalar waves, in a class of spacetimes, namely, the ones generated by a Kerr-Newman-Kasuya spacetime (dyon black hole) and a Reissner-Nordström black hole surrounded by a magnetic field (Ernst spacetime). In both spacetimes, the solutions for the angular and radial parts of the corresponding Klein-Gordon equations are obtained exactly, for massive and massless fields, respectively. The special cases of Kerr and Schwarzschild black holes are analyzed and the solutions obtained, as well as in the case of a Schwarzschild black hole surrounded by a magnetic field. In all these special situations, the resonant frequencies, Hawking radiation and scattering are studied.
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...
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.
Directory of Open Access Journals (Sweden)
Jicheng Wang
2016-01-01
Full Text Available A multiple plasmon-induced transparency (PIT device operated in the mid-infrared region has been proposed. The designed model is comprised of one graphene ribbon as main waveguide and two narrow graphene sheets resonators. The phase coupling between two graphene resonators has been investigated. The multimode PIT resonances have been found in both cases and can be dynamically tuned via varying the chemical potential of graphene resonators without optimizing its geometric parameters. In addition, this structure can get multiple PIT effect by equipping extra two sheets on the symmetric positions of graphene waveguide. The simulation results based on finite element method (FEM are in good agreement with the resonance theory. This work may pave new way for graphene-based thermal plasmonic devices applications.
Upadhyay, Puja; Gustavsson, Jonas P. R.; Alvi, Farrukh S.
2016-05-01
For flow control applications requiring high-frequency excitation, very few actuators have sufficient dynamic response and/or control authority to be useful in high-speed flows. Due to this reason, experiments involving high-frequency excitation, attempted in the past, have been limited to either low-frequency actuation with reasonable control authority or moderate-frequency actuation with limited control authority. The current work expands on the previous development of the resonance-enhanced microactuators to design actuators that are capable of producing high-amplitude pulses at much higher frequencies [{O} (10 kHz)]. Using lumped element modeling, two actuators have been designed with nominal frequencies of 20 and 50 kHz. Extensive benchtop characterization using acoustic measurements as well as optical diagnostics using a high-resolution micro-schlieren setup is employed to characterize the dynamic response of these actuators. The actuators performed at a range of frequencies, 20.3-27.8 and 54.8-78.2 kHz, respectively. In addition to providing information on the actuator flow physics and performance at various operating conditions, this study serves to develop easy-to-integrate high-frequency actuators for active control of high-speed jets. Preliminary testing of these actuators is performed by implementing the 20-kHz actuator on a Mach 0.9 free jet flow field for noise reduction. Acoustic measurements in the jet near field demonstrate attenuation of radiated noise at all observation angles.
Energy Technology Data Exchange (ETDEWEB)
Sklyar, Anna; Ostafin, Michal; Nogaj, Boleslaw [Dept. of Physics, Adam Mickiewicz Univ., Poznan (Poland); Sinyavsky, Nikolay [Baltic State Academy, Kaliningrad (Russian Federation)
2009-09-15
A possibility to excite the spin-3/2 quadrupolar nuclei in sites with a non-zero asymmetry parameter of the electric field gradient (EFG) tensor by means of an elliptically polarized radio frequency (RF) magnetic fields is discussed. Closed analytical formulas for the intensities of nuclear quadrupole resonance (NQR) nutation spectra and nutation, frequencies of powder samples were obtained. Characteristic singularities in the nutation spectra were determined which allow the measurement of the asymmetry parameter {eta}. It was found that in the general case of {eta} {ne} 0 the excitation of the nuclear spins in +m and -m states by using the circularly polarized RF fields is not fully selective. (orig.)
Institute of Scientific and Technical Information of China (English)
ZHANG Shao-hua; YAO Jian-quan; ZHOU Rui; WEN Wu-qi; XU De-gang; WANG Peng
2011-01-01
Using nanosecond pulse near-infrared and mid-infrared laser pulses as the pump source,we obtain terahertz wave sources via four-wave difference frequency mixing.From the coupled wave theory,.we analyze the four-wave mixing process of GaSe crystal and alkali metal vapor in detail,get the analytical expression of terahertz wave output power,and discuss the conditions for achieving phase matching.By adjusting the pump frequency,the third-order nonlinear polarization of alkali metal vapor is resonance-enhanced.This program offers a new type of high-power terahertz radiation source.
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.
Resonant circuit which provides dual-frequency excitation for rapid cycling of an electromagnet
Praeg, W.F.
1982-03-09
Disclosed is a novel ring-magnet control circuit that permits synchrotron repetition rates much higher than the frequency of the sinusoidal guide field of the ring magnet during particle acceleration. The control circuit generates sinusoidal excitation currents of different frequencies in the half waves. During radio-frequency acceleration of the synchrotron, the control circuit operates with a lower frequency sine wave and, thereafter, the electromagnets are reset with a higher-frequency half sine wave.
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.
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.
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 the accuracy of the analysis. The Miller capacitance has been taken into account, and its impact on the performances of the tuned front ends has been demonstrated. The accuracy of the expressions ha...
Muscular adaptations to short-term low-frequency downhill walking training.
Maeo, S; Yamamoto, M; Kanehisa, H
2015-02-01
This study examined muscular adaptations of knee extensors following short-term low-frequency downhill walking training. 22 young males (training group: TG, n=12; control group: CG, n=10) participated. TG conducted 40-min downhill treadmill walking (load: 10% of body mass, gradient: 28%, velocity: 5 km/h) 1 session/week for 4 weeks. Before and after the intervention, muscle thickness of knee extensors and maximal knee extension torques in eccentric (- 120, - 60, - 30°/s), isometric (0°/s), and concentric (30, 60, 120, 240°/s) conditions were measured. For TG, muscle damage markers were also measured before and up to 72 h following each session. After the intervention, CG did not show any changes in all variables. TG had significant increases in maximal knee extension torques at all angular velocities, with higher relative gains in eccentric torques (+ 24% on average) than isometric (+ 13%) and concentric (+ 12% on average) torques. No changes were found in the muscle thickness. Although considerable muscle damage was observed after the first training session in TG, the magnitudes of changes in all markers following the second to fourth sessions were minimal. These results indicate that even with relatively short-term and low-frequency, downhill walking training can increase the strength capacity of knee extensors, especially in eccentric strength.
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)
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...... 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...
Ion cyclotron resonance frequency heating in JET during initial operations with the ITER-like wall
Energy Technology Data Exchange (ETDEWEB)
Jacquet, P., E-mail: philippe.jacquet@ccfe.ac.uk; Monakhov, I.; Arnoux, G.; Brix, M.; Graham, M.; Meigs, A.; Sirinelli, A. [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Bobkov, V.; Devaux, S.; Drewelow, P.; Pütterich, T. [Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Garching (Germany); Colas, L. [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Czarnecka, A. [Association Euratom-IPPLM, Hery 23, 01-497 Warsaw (Poland); Lerche, E.; Van-Eester, D. [Association EURATOM-Belgian State, ERM-KMS, Brussels (Belgium); Mayoral, M.-L. [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); EFDA Close Support Unit, Garching (Germany); Brezinsek, S. [IEK-4, Forschungszentrum Jülich, Association EURATOM-FZJ, Jülich (Germany); Campergue, A.-L. [Ecole Nationale des Ponts et Chaussées, F77455 Marne-la-Vallée (France); Klepper, C. C. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6169 (United States); Milanesio, D. [Politecnico di Torino, Department of Electronics, Torino (Italy); and others
2014-06-15
In 2011/12, JET started operation with its new ITER-Like Wall (ILW) made of a tungsten (W) divertor and a beryllium (Be) main chamber wall. The impact of the new wall materials on the JET Ion Cyclotron Resonance Frequency (ICRF) operation is assessed and some important properties of JET plasmas heated with ICRF are highlighted. A ∼ 20% reduction of the antenna coupling resistance is observed with the ILW as compared with the JET carbon (JET-C) wall. Heat-fluxes on the protecting limiters close the antennas, quantified using Infra-Red thermography (maximum 4.5 MW/m{sup 2} in current drive phasing), are within the wall power load handling capabilities. A simple RF sheath rectification model using the antenna near-fields calculated with the TOPICA code can reproduce the heat-flux pattern around the antennas. ICRF heating results in larger tungsten and nickel (Ni) contents in the plasma and in a larger core radiation when compared to Neutral Beam Injection (NBI) heating. The location of the tungsten ICRF specific source could not be identified but some experimental observations indicate that main-chamber W components could be an important impurity source: for example, the divertor W influx deduced from spectroscopy is comparable when using RF or NBI at same power and comparable divertor conditions, and Be evaporation in the main chamber results in a strong reduction of the impurity level. In L-mode plasmas, the ICRF specific high-Z impurity content decreased when operating at higher plasma density and when increasing the hydrogen concentration from 5% to 15%. Despite the higher plasma bulk radiation, ICRF exhibited overall good plasma heating performance; the power is typically deposited at the plasma centre while the radiation is mainly from the outer part of the plasma bulk. Application of ICRF heating in H-mode plasmas has started, and the beneficial effect of ICRF central electron heating to prevent W accumulation in the plasma core has been observed.
Tsujino, Jiromaru; Hongoh, Misugi; Yoshikuni, Masafumi; Hashii, Hidekazu; Ueoka, Tetsugi
2004-04-01
The welding characteristics of 27, 40 and 67 kHz ultrasonic plastic welding systems that are driven at only the fundamental-resonance frequency vibration were compared, and also those of the welding systems that were driven at the fundamental and several higher resonance frequencies simultaneously were studied. At high frequency, welding characteristics can be improved due to the larger vibration loss of plastic materials. For welding of rather thin or small specimens, as the fundamental frequency of these welding systems is higher and the numbers of driven higher frequencies are driven simultaneously, larger welded area and weld strength were obtained.
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
2017-02-01
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.
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.
A Fixed-Frequency Bidirectional Resonant DC-DC Converter Suitable for Wide Voltage Gain Range
DEFF Research Database (Denmark)
Shen, Yanfeng; Wang, Huai; Al-Durra, Ahmed;
2017-01-01
This paper proposes a new bidirectional resonant dc-dc converter suitable for wide voltage gain range applications (e.g., energy storage systems). The proposed converter overcomes the narrow voltage gain range of conventional resonant DC-DC converters, and meanwhile achieves high efficiency...... and characteristics of the proposed converter are analyzed. Finally, a 1-kW converter prototype is built and the experimental results verify the theoretical analyses....
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.
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. ...
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...
PT-symmetric microring lasers: Self-adapting broadband mode-selective resonators
Hodaei, Hossein; Heinrich, Matthias; Christodoulides, Demetrios N; Khajavikhan, Mercedeh
2014-01-01
We demonstrate experimentally that stable single longitudinal mode operation can be readily achieved in PT-symmetric arrangements of coupled microring resonators. Whereas any active resonator is in principle capable of displaying single-wavelength operation, selective breaking of PT-symmetry can be utilized to systematically enhance the maximum achievable gain of this mode, even if a large number of competing longitudinal or transverse resonator modes fall within the amplification bandwidth of the inhomogeneously broadened active medium. This concept is robust with respect to fabrication tolerances, and its mode selectivity is established without the need for additional components or specifically designed filters. Our results may pave the way for a new generation of versatile cavities lasing at a desired longitudinal resonance. Along these lines, traditionally highly multi-moded microring resonator configurations can be fashioned to suppress all but one longitudinal mode.
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
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)
Lars Neeb
2013-08-01
Full Text Available Background: The main safety aspect in the use of stroke thrombolysis and in clinical trials of new pharmaceutical or interventional stroke therapies is the incidence of hemorrhagic transformation (HT after treatment. The computed tomography (CT-based classification of the European Cooperative Acute Stroke Study (ECASS distinguishes four categories of HTs. An HT can range from a harmless spot of blood accumulation to a symptomatic space-occupying parenchymal bleeding associated with a massive deterioration of symptoms and clinical prognosis. In magnetic resonance imaging (MRI HTs are often categorized using the ECASS criteria although this classification has not been validated in MRI. We developed MRI-specific criteria for the categorization of HT and sought to assess its diagnostic reliability in a retrospective study. Methods: Consecutive acute ischemic stroke patients, who had received a 3-tesla MRI before and 12-36 h after thrombolysis, were screened retrospectively for an HT of any kind in post-treatment MRI. Intravenous tissue plasminogen activator was given to all patients within 4.5 h. HT categorization was based on a simultaneous read of 3 different MRI sequences (fluid-attenuated inversion recovery, diffusion-weighted imaging and T2* gradient-recalled echo. Categorization of HT in MRI accounted for the various aspects of the imaging pattern as the shape of the bleeding area and signal intensity on each sequence. All data sets were independently categorized in a blinded fashion by 3 expert and 3 resident observers. Interobserver reliability of this classification was determined for all observers together and for each group separately by calculating Kendall's coefficient of concordance (W. Results: Of the 186 patients screened, 39 patients (21% had an HT in post-treatment MRI and were included for the categorization of HT by experts and residents. The overall agreement of HT categorization according to the modified classification was
Directory of Open Access Journals (Sweden)
Hani Vahedi
2011-01-01
Full Text Available Hysteresis Current Control (HCC is widely used due to its simplicity in implementation, fast and accurate response. However, the main issue is its variable switching frequency which leads to extraswitching losses and injecting high-frequency harmonics into the system current. To solve this problem, adaptive hysteresis current control (AHCC has been introduced which produces hysteresis bandwidth which instantaneously results in smoother and constant switching frequency. In this paper the instantaneous power theory is used to extract the harmonic components of system current. Then fixed-band hysteresis current control is explained. Because of fixed-band variable frequency disadvantages, the adaptive hysteresis current control is explained that leads to fixing the switching frequency and reducing the high-frequency components in source current waveform. Due to these advantages of AHCC, the switching frequency and switching losses will be diminished appropriately. Some simulations are done in MATLAB/Simulink. The Fourier Transform and THD results of source and load currents and the instantaneous switching frequency diagram are discussed to prove the efficiency of this method. The Fourier Transform and THD results of source and load currents are discussed to prove the validity of this method.
Phuoc, Nguyen N.; Ong, C. K.
2016-10-01
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.
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...
Venosa, Elettra; Vermeire, Bert; Alakija, Cameron; Harris, Fred; Strobel, David; Sheehe, Charles J.; Krunz, Marwan
2017-01-01
In the last few years, radio technologies for unmanned aircraft vehicle (UAV) have advanced very rapidly. The increasing need to fly unmanned aircraft systems (UAS) in the national airspace system (NAS) to perform missions of vital importance to national security, defense, and science has pushed ahead the design and implementation of new radio platforms. However, a lot still has to be done to improve those radios in terms of performance and capabilities. In addition, an important aspect to account for is hardware cost and the feasibility to implement these radios using commercial off-the-shelf (COTS) components. UAV radios come with numerous technical challenges and their development involves contributions at different levels of the design. Cognitive algorithms need to be developed in order to perform agile communications using appropriate frequency allocation while maintaining safe and efficient operations in the NAS and, digital reconfigurable architectures have to be designed in order to ensure a prompt response to environmental changes. Command and control (C2) communications have to be preserved during "standard" operations while crew operations have to be minimized. It is clear that UAV radios have to be software-defined systems, where size, weight and power consumption (SWaP) are critical parameters. This paper provides preliminary results of the efforts performed to design a fully digital radio architecture as part of a NASA Phase I STTR. In this paper, we will explain the basic idea and technical principles behind our dynamic/adaptive frequency hopping radio for UAVs. We will present our Simulink model of the dynamic FH radio transmitter design for UAV communications and show simulation results and FPGA system analysis.
Liu, Guoxi; Li, Xiaotian; Chen, Jianguo; Shi, Huaduo; Xiao, Wenlei; Dong, Shuxiang
2012-10-01
Colossal low-frequency resonant magnetomechanical (MM) and magnetoelectric (ME) coupling effects have been found in a three-phase composite made of Pb(Zr,Ti)O3 ceramic fibers/phosphor copper-sheet unimorph and NdFeB magnets. The experimental results revealed that the ferromagnetic/elastic/piezoelectric three-phase composite with a cantilever beam structure could show huge bending MM coefficient of ˜145.9 × 10-3/Oe (unit in bending radian per Oe) and ME voltage coefficient of ˜16 000 V/cm.Oe at the first-order bending resonance frequency of ˜5 Hz. The achieved results related to ME effect are at least one order of magnitude higher over those of other ME materials and devices reported ever. The extremely strong MM and ME couplings in the three-phase composite are due to strong magnetic force moment effect induced by the interaction between NdFeB magnets and the applied magnetic field, and further resonant enhancement via the strain-mediated phosphor copper-sheet with a relatively high mechanical quality factor.
Energy Technology Data Exchange (ETDEWEB)
Johannsmann, Diethelm
2001-06-01
Viscoelastic effects contribute to the shift in resonance frequency of quartz crystal resonators induced by deposition of thin films on the resonator surface. In turn, the mechanical stiffness of the film can be experimentally determined from a comparison of the resonance shifts on different harmonics. When the film is much thinner than the wavelength of shear sound, a series expansion of the viscoelastic effects to third order in film thickness leads to rather simple equations. When plotting the normalized frequency shift {delta}f/f versus the square of the overtone order n{sup 2} one finds a linear relationship, where the slope is determined by the film{close_quote}s elastic compliance. When the same analysis is carried out on the resonance bandwidths rather than the frequency shifts the viscous compliance is obtained. The effects of asymmetric coatings, electrodes, and liquid media are discussed. {copyright} 2001 American Institute of Physics.
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.
Directory of Open Access Journals (Sweden)
Shaohua Luo
2016-04-01
Full Text Available This paper addresses chaos control of the micro-electro- mechanical resonator by using adaptive dynamic surface technology with extended state observer. To reveal the mechanism of the micro- electro-mechanical resonator, the phase diagrams and corresponding time histories are given to research the nonlinear dynamics and chaotic behavior, and Homoclinic and heteroclinic chaos which relate closely with the appearance of chaos are presented based on the potential function. To eliminate the effect of chaos, an adaptive dynamic surface control scheme with extended state observer is designed to convert random motion into regular motion without precise system model parameters and measured variables. Putting tracking differentiator into chaos controller solves the ‘explosion of complexity’ of backstepping and poor precision of the first-order filters. Meanwhile, to obtain high performance, a neural network with adaptive law is employed to approximate unknown nonlinear function in the process of controller design. The boundedness of all the signals of the closed-loop system is proved in theoretical analysis. Finally, numerical simulations are executed and extensive results illustrate effectiveness and robustness of the proposed scheme.
Luo, Shaohua; Sun, Quanping; Cheng, Wei
2016-04-01
This paper addresses chaos control of the micro-electro- mechanical resonator by using adaptive dynamic surface technology with extended state observer. To reveal the mechanism of the micro- electro-mechanical resonator, the phase diagrams and corresponding time histories are given to research the nonlinear dynamics and chaotic behavior, and Homoclinic and heteroclinic chaos which relate closely with the appearance of chaos are presented based on the potential function. To eliminate the effect of chaos, an adaptive dynamic surface control scheme with extended state observer is designed to convert random motion into regular motion without precise system model parameters and measured variables. Putting tracking differentiator into chaos controller solves the `explosion of complexity' of backstepping and poor precision of the first-order filters. Meanwhile, to obtain high performance, a neural network with adaptive law is employed to approximate unknown nonlinear function in the process of controller design. The boundedness of all the signals of the closed-loop system is proved in theoretical analysis. Finally, numerical simulations are executed and extensive results illustrate effectiveness and robustness of the proposed scheme.
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.
Influence of Resistance Training Frequency on Muscular Adaptations in Well-Trained Men.
Schoenfeld, Brad J; Ratamess, Nicholas A; Peterson, Mark D; Contreras, Bret; Tiryaki-Sonmez, Gul
2015-07-01
The purpose of this study was to investigate the effects of training muscle groups 1 day per week using a split-body routine (SPLIT) vs. 3 days per week using a total-body routine (TOTAL) on muscular adaptations in well-trained men. Subjects were 20 male volunteers (height = 1.76 ± 0.05 m; body mass = 78.0 ± 10.7 kg; age = 23.5 ± 2.9 years) recruited from a university population. Participants were pair matched according to baseline strength and then randomly assigned to 1 of the 2 experimental groups: a SPLIT, where multiple exercises were performed for a specific muscle group in a session with 2-3 muscle groups trained per session (n = 10) or a TOTAL, where 1 exercise was performed per muscle group in a session with all muscle groups trained in each session (n = 10). Subjects were tested pre- and poststudy for 1 repetition maximum strength in the bench press and squat, and muscle thickness (MT) of forearm flexors, forearm extensors, and vastus lateralis. Results showed significantly greater increases in forearm flexor MT for TOTAL compared with SPLIT. No significant differences were noted in maximal strength measures. The findings suggest a potentially superior hypertrophic benefit to higher weekly resistance training frequencies.
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.
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.).
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.
Development of Integrated Electronics for Readout of High Frequency Micro/Nano-mechanical Resonator
DEFF Research Database (Denmark)
Tang, Meng
Micro størrelse bulk type resonatorer er blevet udviklet gennern de sidste fem år til anvendelse inden for elektronikbranchen til lav strøm og billige alternativer til både passive og aktive komponenter. Dog kan denne type bulk resonator også bruges til bio/kemiske sensorer hvor, da på grund af den...
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...... expression can be used to the estimate influence of system parameters, and to plan and interpret laboratory experiments....
Selecting the optimum engineering model for the frequency response of fcc nanowire resonators
DEFF Research Database (Denmark)
Nasr Esfahani, M.; Yilmaz, M.; Sonne, Mads Rostgaard
2016-01-01
such as the nanowire resonators. The success of the engineer- ing design of such miniaturized systems will depend heavily on the availability of accu- rate mechanistic models with the least possible computational cost. Although a variety of models are available for this purpose, the boundaries between their admissible...
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.
Ultra-pure RF tone from a micro-ring resonator based optical frequency comb source
Pasquazi, Alessia; Little, Brent E; Chu, Sai T; Moss, David J; Morandotti, Roberto
2014-01-01
We demonstrate a novel mode locked ultrafast laser, based on an integrated high-Q micr-oring resonator. Our scheme exhibits stable operation of two slightly shifted spectral optical comb replicas. It generates a highly monochromatic radiofrequency modulation of 60MHz on a 200GHz output pulse train, with a linewidth < 10kHz
Resonant circuit which provides dual frequency excitation for rapid cycling of an electromagnet
Praeg, Walter F.
1984-01-01
Disclosed is a ring magnet control circuit that permits synchrotron repetition rates much higher than the frequency of the cosinusoidal guide field of the ring magnet during particle acceleration. the control circuit generates cosinusoidal excitation currents of different frequencies in the half waves. During radio frequency acceleration of the particles in the synchrotron, the control circuit operates with a lower frequency cosine wave and thereafter the electromagnets are reset with a higher frequency half cosine wave. Flat-bottom and flat-top wave shaping circuits maintain the magnetic guide field in a relatively time-invariant mode during times when the particles are being injected into the ring magnets and when the particles are being ejected from the ring magnets.
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...
Energy Technology Data Exchange (ETDEWEB)
Sadinezhad, I.; Joorabian, M. [Electrical Engineering Department, Shahid Chamran University, Ahvaz 61355 (Iran)
2009-08-15
This paper presents the application of a Complex Adaptive Linear Neural Network (CADALINE) in tracking the fundamental power system frequency. In this method, by using stationary-axes Park transformation in addition to producing a complex input measurement, the decaying DC offset is eliminated. As the proposed method uses first-order differentiator to estimate frequency changes, a Hamming filter is used to smoothen the response and cancel high-frequency noises. The most distinguishing features of the proposed method are the reduction in the size of observation state vector required by a simple Adaptive Linear Neural Network (ADALINE) and increase in the accuracy and convergence speed under transient conditions. This paper concludes with the presentation of the representative results obtained in numerical simulation and simulation in PSCAD/EMTDC software as well as in practical study. (author)
Park, Harold S
2009-03-18
There are two major objectives to the present work. The first objective is to demonstrate that, in contrast to predictions from linear surface elastic theory, when nonlinear, finite deformation kinematics are considered, the residual surface stress does impact the resonant frequencies of silicon nanowires. The second objective of this work is to delineate, as a function of nanowire size, the relative contributions of both the residual (strain-independent) and the surface elastic (strain-dependent) parts of the surface stress to the nanowire resonant frequencies. Both goals are accomplished by using the recently developed surface Cauchy-Born model, which accounts for nanoscale surface stresses through a nonlinear, finite deformation continuum mechanics model that leads to the solution of a standard finite element eigenvalue problem for the nanowire resonant frequencies. In addition to demonstrating that the residual surface stress does impact the resonant frequencies of silicon nanowires, we further show that there is a strong size dependence to its effect; in particular, we find that consideration of the residual surface stress alone leads to significant errors in predictions of the nanowire resonant frequency, with an increase in error with decreasing nanowire size. Correspondingly, the strain-dependent part of the surface stress is found to have an increasingly important effect on the resonant frequencies of the nanowires with decreasing nanowire size.
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.
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.
Cyclotron mode frequencies and resonant absorption in multi-species ion plasmas
Energy Technology Data Exchange (ETDEWEB)
Affolter, M.; Anderegg, F.; Dubin, D. H. E.; Driscoll, C. F. [Department of Physics, University of California at San Diego, La Jolla, California 92093 (United States)
2015-05-15
Cyclotron mode frequencies are studied on trapped rigid-rotor multi-species ion plasmas. Collective effects and radial electric fields shift the mode frequencies away from the “bare” cyclotron frequencies 2πF{sub c}{sup (s)}≡(q{sub s}B/M{sub s}c) for each species s. These frequency shifts are measured on the distinct cyclotron modes (m=0,1, and 2) with cos(mθ) azimuthal dependence. We find that for radially uniform plasmas the frequency shifts corroborate a simple theory expression, in which collective effects enter only through the E × B rotation frequency f{sub E} and the species fraction δ{sub s}. The m = 1 center-of-mass mode is in agreement with a simple “clump” model. Additionally, ultra-cold ion plasmas exhibit centrifugal separation by mass, and additional frequency shifts are observed, in agreement with a more general theory.
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.
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
Vocal tract motor patterns and resonance during constant frequency song: the white-throated sparrow
Riede, Tobias; Suthers, Roderick A.
2008-01-01
Bird song is a complex behavior that requires the coordination of several motor systems. Sound is produced in the syrinx and then modified by the upper vocal tract. Movements of the hyoid skeleton have been shown in the northern cardinal (Cardinalis cardinalis) to be extensively involved in forming an oropharyngeal–esophageal cavity (OEC), which contributes a major resonance to the vocal tract transfer function. Here we report that a similar relationship exists between the volume of the OEC a...