Collective vibrational resonance and mode selection in nonlinear resonator arrays.

Parametric excitation of traveling waves in a circular non-dispersive medium

The electrical activities of neurons are dependent on the complex electrophysiological condition in neuronal system, the three-variable Hindmarsh-Rose (HR) neuron model is improved to describe the dynamical behaviors of neuronal activities with electromagnetic induction being considered, and the mode transition of electrical activities in neuron is detected when external electromagnetic radiation is imposed on the neuron. In this paper, different types of electrical stimulus impended with a high-low frequency current are imposed on new HR neuron model, and mixed stimulus-induced mode selection in neural activity is discussed in detail. It is found that mode selection of electrical activities stimulated by high-low frequency current, which also changes the excitability of neuron, can be triggered owing to adding the Gaussian white noise. Meanwhile, the mode selection of the neuron electrical activity is much dependent on the amplitude B of the high frequency current under the same noise intensity, and the high frequency response is selected preferentially by applying appropriate parameters and noise intensity. Our results provide insights into the transmission of complex signals in nerve system, which is valuable in engineering prospective applications such as information encoding.

We investigate the hypothesis that intrafascicular stimulation of the pudendal nerve (PN) can be used to selectively activate the detrusor bladder muscle and the external urethral sphincter (EUS). Nine anesthetized male canines were used in this study. Muscle activations were measured via bladder catheter pressure transducers and EUS electromyography (EMG) wires. The PNs were exposed via dissection of the ischioanal fossa and implanted with Utah Slanted Electrode Arrays (USEAs). USEAs consist of 100, 0.5–1.5 mm long microelectrodes that project out from a 4 $\,\times\,$ 4 mm substrate. Intrafascicular stimulation was delivered via individual USEA microelectrodes in order to map the ability of each electrode to selectively or nonselectively evoke detrusor and/or EUS contractions. We were able to selectively activate the detrusor using 33 Hz stimulation of PN axons with an average of $4.57 \pm 3.82$ ( ${\rm mean }\pm {\rm sd}$ ) USEA electrodes per animal tested. Electrically-evoked and distention-evoked bladder contractions had similar kinetics. Sustained bladder contractions were evoked via 60 s of intrafascicular stimulation. The EUS was activated using 33 Hz stimulation via an average of $26.14 \pm 19.45$ electrodes per animal tested. High frequency ( $> {2}~{\rm kHz}$ ) stimulation delivered via EUS selective electrodes produced nonselective block of PN axons. Examples of how this selective axonal access could be used to restore continence and activate micturition were demonstrated in two animals. We report herein the first study demonstrating selective detrusor and EUS activation via microelectrodes implanted intrafascicularly in the PN. Such selective activation enables new therapeutic possibilities for controlling the muscles of micturition.

In this paper, we propose an approach to manipulate a translation-invariant single-band tight-binding system beyond nearest-neighbor coupling. By using a sequence of multiple identical pulsed electric fields with specific strengths and calculated intervals, the propagator of the system can be fully controlled within an infinite space with dimensions given by the configuration of existing nonzero couplings. And if the sequence is repeated, the system evolution can then effectively simulate another system with a different array of hopping energies, provided that these hopping energies are already nonzero in the simulator. Moreover, the effective system's response to a wide range of additional influences, which are not required to be small, is also shown to approach that of the system it simulates in the limit of high kicking frequency. The simulation is therefore robust and the simulator can potentially be indistinguishable from the lattice it simulates. Considering the physical simplicity, this approach cannot only realize flexible experimental platforms for lattices beyond nearest-neighbor coupling, it is also potentially applicable to the manipulation of actual materials.

Controlling the modal content coupled into an optical fiber can be desireable\nin many situations, e.g. for adjusting the sensitivity of the guided field\ndistribution to external perturbations. For this purpose we used a monolithic\nsetup of a phase plate at a fiber inpute facet to excite selectivly higher\norder modes, which theoretically can provide a mode purity of more than 99%. We\ninvestigated the capabilities of this approach by complete modal decomposition\nof the fiber output signals, considering the achievable mode purity with\nrespect to several possible imperfections of the setup. The experiments are\ncompared with detailed numerical simulations and show a high agreement.\nAdditionally a comparison with a well known setup with free space phase plates\nwas undertaken. This showed the monolithic setup to be energetically twice as\nefficient.\n

Analysis of time-varying mechanical systems using the method of impulsive parametric excitation

Mode selective transmission line is one of the potential solutions for the increasing demand of high-speed transmission rate. In this paper, a multi-mode waveguide with mode selective effect is proposed. The proposed waveguide can operate with transverse electromagnetic (TEM) mode over low frequency, which is similar to a parallel plate waveguide, and TE 10 mode over high frequency, which is similar to a substrate integrate waveguide (SIW). To verify the mode selective effect of the multi-mode waveguide, the multi-mode waveguide is designed and fabricated in printed circuit board (PCB) process. The electric field distribution and the variation of the attenuation constant with frequency show that the mode selection occurs around the cutoff frequency of the TE 10 mode of the multi-mode waveguide. The measurement results of the S-parameters and the propagation constant agree well with the simulation ones in the range of DC-30GHz.

High-frequency vibrational control of principal parametric resonance of a nonlinear cantilever beam: Theory and experiment

We examine and analyze vibrational resonance (VR) in a dual-frequency-driven gyroscope subject to a parametric excitation and an additive periodic forces. The method of direct separation of the fast and slow motions is used to derive the response amplitude analytically from the equation for slow oscillations of the system, in terms of the parameters of the high-frequency signal and the parametric excitation. Numerical simulations are carried out to validate the theoretical results. It is further shown that, when the parametric excitation and additive periodic force consist of low and high frequencies, respectively, a much higher response amplitude can occur. It is about three times larger than the response obtained when the forcing actions are reversed and is attributable to the optimization of low-frequency parametric excitation by the high-frequency additive signal.

A novel average inductor current sensing circuit integrable in CMOS technologies is presented. It is designed for DC---DC converters using buck, boost, or buck-boost topologies and operating in continuous conduction mode at high switching frequencies. The average inductor current value is used by the DC---DC controllers to increase the light load power conversion efficiency (e.g., selection of the modulation mode, selection of the dynamic width of the transistors). It can also be used to perform the constant current charging phase when charging lithium-ion batteries, or to simply detect overcurrent faults. The proposed average inductor current sensing method is based on the lossless sensing MOSFET principle widely used in monolithic CMOS integrated DC---DC converters for measuring the current flowing through the power switches. It consists of taking a sample of the current flowing through the power switches at a specific point in time during each energizing and de-energizing cycle of the inductor. By controlling precisely the point in time at which this sample is taken, the average inductor current value can be sensed directly. The circuit simulations were done with the Cadence Spectre simulator. The improvements compared to the basic sensing MOSFET principle are a lower power consumption because no high bandwidth amplifier is required, and less noise emission because the sensing MOSFET is no more switched. Additionally, the novel average inductor current sensing circuit overcomes the low bandwidth limitation previously associated with the sensing MOSFET principle, thus enabling it to be used in DC---DC converters operating at switching frequencies up to 10 MHz and above.

This paper summarizes Air Mobility Command's (AMC's) non-developmental airlift aircraft (NDAA) avionics requirements, information gleaned from surveys of the aeronautical community without attribution, and an assessment of potential air traffic control (ATC) and command and control (C/sup 2/) avionics that would provide the necessary capabilities to meet NDAA objectives. Communications capabilities may include Inmarsat-Aero and military ultra high frequency (UHF) satellite communications (SATCOM); air/ground very high frequency (VHF) and UHF; military high frequency (HF) and HF data link; and provisioning for the aeronautical telecommunications network (ATN) protocols for interconnecting satellite, Mode Select (S), VHF, and possibly HF terminals. Navigation and precision landing systems are also discussed. Looking towards future communications, navigation, surveillance/air traffic management (CNS/ATM) concepts, another theme of the paper is preplanned product improvements (P/sup 3/I) leading to increased performance capabilities as new avionics and operational procedures become available. The ultimate goal is the ability to participate in free flight, a concept that will be described as the CNS/ATM vision of the future.

We examine the response of a system of coupled nonlinear oscillators driven by a rapidly varying field, to a low frequency weak periodic excitation of one of the oscillators. The response amplitude of the weak field-driven oscillator at an optimal strength of the rapidly varying field exhibits a strong suppression accompanied by a large negative shift in its oscillation phase. The minimum can be identified as vibrational antiresonance in between the two maxima corresponding to vibrational resonance. This vibrational antiresonance can be observed only in nonlinear coupled systems and not in linearly coupled systems or in a single nonlinear oscillator, under similar physical condition. We discuss the underlying dynamical mechanism, the role of nonlinearity and high frequency in characterizing this counter-resonance effect. Our theoretical analysis is corroborated by detailed numerical simulations.

Detailed numerical simulations have been performed to study the effect of flow orientation with respect to gravity on two-phase flow heat transfer (without phase change) in small diameter pipes. The Nusselt number distribution shows that the bubbly, slug, and slug-train regimes transport as much as three to four times more heat from the tube wall to the bulk flow than pure water flow. The flow blockage effect of the inclusions results in a circulating liquid flow superimposed on the mean flow. For upflow, the breakup into bubbles/slugs occurs earlier and at a higher frequency. The average Nusselt numbers are not significantly affected by the flow orientation with respect to gravity. A mechanistic heat transfer model based on frequency and length scale of inclusions is also presented.

Dihydrofolate reductase (DHFR) and thymidylate synthase (TS) activities are associated with a 285,000 molecular weight enzyme complex in carrot (Daucus carota L.). Selection for methotrexate (MTX) resistance by stepwise increase of the concentration of MTX results in a high frequency adaptation to MTX with little or no significant increase in DHFR activity. However, when as a second step following MTX selection a specific inhibitor of TS, 5-fluoro-2-deoxyuridine was used, DHFR overproducer lines were obtained. The overproduction phenotype of the lines was almost completely lost after 8 weeks of growth in the absence of selection pressure. Although DHFR and TS are independent gene products, their activities increase in proportion ( approximately 20-fold) in the overproducer lines. This strongly suggests that DHFR and TS are not only functionally and physically linked in the same enzyme complex, but also are coregulated. These cell lines resemble the MTX-induced DHFR overproducer amplified cell lines of mammalian origin in their mode of selection, high frequency of appearance, elevated enzyme activity, and increased specific mRNA levels.

Study on noise control effect based on generalized Lorenz system