Variation Of Resonant Frequency Research Articles

An Estimation of Resonant Frequency of a Curving RFID Tag

Radio frequency identification (RFID) technology may be applied to cylindrical objects, but the curving of an RFID tag brings on an increase in resonant frequency of the tag antenna. The tag can not function in an excessively curving case, since the deviation of the antenna resonant frequency from working frequency makes a reduction in inductive energy supplied by a transmitter. The variation in antenna resonant frequency is dependant upon column radius of the cylinder and curving angle of the tag. Analytically, it is found that a reduction in central distance, which is determined by column radius and curving angle, between compound straight tracks leads to the decreasing of overall antenna-coil inductance after the curving of the tag. By introducing a curving turn exponent, the overall antenna-coil inductance is calculated. After neglecting the less variation in overall tag capacitance, the antenna resonant frequency may be estimated. The result provides an instruction for designing a curving tag antenna to fit the tag antenna resonant frequency for working frequency of an RFID system.

Experimental synthesis of seismic horizontal free-field motion of soil in finite-domain simulations with absorbing boundary

In this paper, a fundamental assessment of the method of physical wave-absorbing boundary and centrifuge modeling is presented in the context of experimental simulations of seismic free-field ground motion. Focusing on the characteristics of a sand stratum, a series of seismic tests on models of uniform density and a large width-to-depth ratio with Duxseal as the side boundary were performed using an in-box shake-table system. By means of the transfer function approach in the frequency domain, the complex three-dimensional nature of the dynamic response of the finite soil model with the boundary treatment is demonstrated in terms of its variable resonant frequency distribution at different g-levels. Apart from being helpful in quantifying the difficulty in interpreting the finite-domain response simulations using one-dimensional theories or homogenized representations, the measured data substantiates the need and usefulness of coupling the Duxseal boundary approach with a three-dimensional elastodynamic synthesis. With the aid of a corresponding boundary element implementation, the feasibility of identifying the soil's in-flight shear modulus variation, Poisson's ratio and horizontal-to-vertical earth pressure ratio from the centrifuge model's free-field measurements is also explored.

Seismic characterization and monitoring of Fucino Basin (Central Italy)

The Fucino basin (Central Italy) is one of the largest intramountain alluvial plain in the Apennines range. It has a tectonic origin related to the presence of important systems of faults located in its northern and eastern edges. Some of these faults are still active and capable of generating strong seismic events. Site effects related to the soft soils filling the basin can be very important. In this paper we show the preliminary results of a seismic network installed in the Fucino area in order to collect information about site amplification effects and geometry of the basin. We analyze ambient seismic vibrations and recordings of about 150 local earthquakes mainly related to the seismic sequence of the April 6th 2009 Mw 6.3 L’Aquila event. Moreover the strongest events of L’Aquila sequence were analyzed at the three permanent strong-motion stations operating in the area. Using standard spectral techniques we investigate the variation of resonance frequencies within the basin. The ground motion recorded in the Fucino plain is mainly characterized by strong energy at low-frequencies (f < 1 Hz) affecting both horizontal and vertical components. This is particularly evident for stations deployed in correspondence of very thick deposits of sedimentary filling, where a significant increase of ground-motion amplitude and duration is likely caused by locally generated surface waves. The amplification at low-frequencies (<1 Hz) on the horizontal components can reach up a factor of 10 in comparison to nearby stiff sites. However, we found evidences of seismic amplification phenomena also for stiff sites surrounding the basin, including stations of the Italian strong motion network. The independent geological information and the shallow shear-velocity profiles available for the basin can be combined with resonance frequencies for deriving representative geological sections to be used as base for future numerical 2D–3D modeling of the basin.

Functional advances of microwave dielectrics for next generation

In coming age, new technologies for survivals of human beings on our earth are required. These technologies include for energy and natural resources conservation, waste disposal techniques, and reduction of global warming gases. To achieve this advanced functions of materials are essential. In this paper, new frontiers of microwave dielectrics are presented in relations with these energy issues. The microwave dielectrics are familiar with radio frequency wave. The low loss dielectric materials are resonated by microwaves in air and change it to electric current in circuit, and vice versa. It is well known that the microwave materials have three important characteristic properties such as high quality factor Q, dielectric constant ɛ r and temperature coefficient of resonant frequency TCf. These properties enable the following functions: (1) electromagnetic resonance, (2) electromagnetic-wave shortening, (3) electromagnetic-wave delay, (4) temperature variation of resonant frequency, (5) electromagnetic-wave absorption, and (6) other functions: such as transparency and refractive index. In this paper, for future excellent usages of these functions, some applications are presented showing the fundamental explanations. The content in this paper is planned for the publication in a handbook of advancements of functional ceramics.

Integral Resonant Control for Vibration Damping and Precise Tip-Positioning of a Single-Link Flexible Manipulator

In this paper, we propose a control design method for single-link flexible manipulators. The proposed technique is based on the integral resonant control (IRC) scheme. The controller consists of two nested feedback loops. The inner loop controls the joint angle and makes the system robust to joint friction. The outer loop, which is based on the IRC technique, damps the vibration and makes the system robust to the unmodeled dynamics (spill-over) and resonance frequency variations due to changes in the payload. The objectives of this work are: 1) to demonstrate the advantages of IRC, which is a high-performance controller design methodology for flexible structures with collocated actuator-sensor pairs and 2) to illustrate its capability of achieving precise end-point (tip) positioning with effective vibration suppression when applied to a typical flexible manipulator. The theoretical formulation of the proposed control scheme, a detailed stability analysis and experimental results obtained on a flexible manipulator are presented.

Electric tunability of microwave permeability dispersion behaviors of metamaterials

By embedding a capacity-variable diode into a split ring resonator (SRR), it is found that the effective capacitance of such an SRR element can be varied by the biased voltage of diode. Therefore the resonance frequency and effective permeability of an SRR element can be tuned. Based on these results, a smart microwave magnetic metamaterial is proposed. Employing the finite-difference time-domain and retrieval method, the variations of resonance frequency and permeability of the SRR element are simulated and calculated by changing the biased voltage. It is found that with the decrease of capacitance due to the increase of biased voltage, the resonance frequencies are shifted towards lower values, and so are the resonance frequencies of permeability dispersion. Finally, the difference in permeability dispersion behavior between SRR structure and natural magnetic material (for instance, ferrite) has been pointed out.

共振周波数変動と制御入力振幅の制約を考慮した適応型有限ステップ整定フィードフォワード補償

共振周波数変動と制御入力振幅の制約を考慮した適応型有限ステップ整定フィードフォワード補償

Resonance frequency distribution of cantilevered (5,5)(10,10) double-walled carbon nanotube with different intertube lengths

Analysis of ultrahigh frequency nanomechanical resonators, which are based on double-walled carbon nanotubes (DWCNTs) with various wall lengths, was carried out via classical molecular dynamics simulations. In the case of the inner wall entirely encapsulated inside the outer wall, the outer wall vibration has a significant effect on the vibration of the DWCNT; while in the case of the inner wall longer than the outer wall, the vibration of the extruded inner wall has a substantially stronger effect on the DWCNT vibration. It is shown that variations of the DWCNT resonance frequency with different wall lengths can be well fitted by Pearson VII and Gauss distribution functions. This result is potentially useful for developing design guidelines for making very fine tuners using DWCNT resonators of various wall lengths.

The effect of pinhole defect on vibrational characteristics of single walled carbon nanotube

Carbon nanotubes are widely used in the design of nano sensors and actuators. Any defect in the manufactured nanotube affects its sensing performance and also influences its dynamic behavior. In this paper, the effect of pinhole defects on the dynamic characteristics of carbon nanotubes is investigated using continuum mechanics and the molecular structural mechanics approach. Dynamic analysis is performed for achiral nanotubes using the continuum mechanics approach with cantilever boundary condition, while for chiral nanotubes the molecular structural mechanics method is used. The shift of the principal frequency of the nanotube with number of pinhole defects on the length is observed and analyzed. The simulation results indicate that the existence of defects mostly affects the resonant frequency (bending rigidity) of single walled carbon nanotubes as the number of defects (pinhole) increase. Further, it is also observed that with the reduction in tube length, the variations in resonant frequency are enhanced. However, it is found that the frequency variation is less sensitive to the nanotube diameter.

Dynamic response of the Chamousset rock column (Western Alps, France)

This paper investigates the variation of the first resonance frequency of the Chamousset limestone column (21,000 m3, Vercors, French Alps) before its collapse in November 2007. The site was instrumented with seismometers and extensometers during a 4‐month period with some gaps in the measurements. Experimental results and numerical modeling showed that the resonance frequency of a prone‐to‐fall column can be derived from the spectra of continuous seismic noise records. At the Chamousset site, the evolution of the resonance frequency appeared to be strongly controlled by the temperature. When temperatures were positive, slight resonance frequency variations correlated well with thermal fluctuations. Irreversible damage can occur during freeze‐thaw cycles and to a lesser extent during strong wind. It coincided with a significant drop in resonance frequency, which was interpreted as the result of rock bridge breakage. This hypothesis is supported by fresh rupture observations after the collapse, seismic event records, and numerical modeling. This study suggests that seismic noise recording could be used for assessing the potential failure of unstable columns in rigid rocks.

콘크리트의 탄성계수 및 감쇠비 결정에 대한 충격공진시험 적용

콘크리트의 탄성계수 결정을 위해 다양한 시험기법이 사용되고 있다. 충격공진시험(IR: impact resonance test)은 비파괴시험으로서 간편한 시험장치와 단순한 시험방법이며 반복성이 뛰어나다. 또한 충격공진시험은 탄성계수 뿐만 아니라 감쇠비 결정이 가능하다. 이 연구에서는 콘트리트 시편에 대한 충격공진시험의 다양한 영향요소(시편거치 방법, 충격하중원의 특성, 신호획득 속도 등)를 평가하고 최적의 시험조건을 제시하였다. 이 연구에서 적용한 모든 시험조건 범위에서 충격공진시험에서 측정된 결과의 변동량은 공진주파수 결정에 있어서 ±0.3%, 감쇠비 결정에 있어서 ±10.0%로 나타났다. 충격공진시험에서 결정된 탄성계수와 정적시험에서 결정된 탄성계수를 변형률 크기를 고려하여 비교하면 비교적 서로 잘 일치함을 확인하였다.

Silicon photonics manufacturing

Most demonstrations in silicon photonics are done with single devices that are targeted for use in future systems. One of the costs of operating multiple devices concurrently on a chip in a system application is the power needed to properly space resonant device frequencies on a system's frequency grid. We asses this power requirement by quantifying the source and impact of process induced resonant frequency variation for microdisk resonators across individual die, entire wafers and wafer lots for separate process runs. Additionally we introduce a new technique, utilizing the Transverse Electric (TE) and Transverse Magnetic (TM) modes in microdisks, to extract thickness and width variations across wafers and dice. Through our analysis we find that a standard six inch Silicon on Insulator (SOI) 0.35 μm process controls microdisk resonant frequencies for the TE fundamental resonances to within 1 THz across a wafer and 105 GHz within a single die. Based on demonstrated thermal tuner technology, a stable manufacturing process exhibiting this level of variation can limit the resonance trimming power per resonant device to 231 μW. Taken in conjunction with the power to compensate for thermal environmental variations, the expected power requirement to compensate for fabrication-induced non-uniformities is 17% of that total. This leads to the prediction that thermal tuning efficiency is likely to have the most dominant impact on the overall power budget of silicon photonics resonator technology.

Improved constraints on isotropic shift and anisotropies of the speed of light using rotating cryogenic sapphire oscillators

We demonstrate that Michelson-Morley tests, which detect direction-dependent anisotropies in the speed of light, can also be used to place limits upon isotropic deviations of the vacuum speed of light from $c$, as described by the photon sector Standard Model Extension (SME) parameter $\tilde{\kappa}_{tr}$. A shift in the speed of light that is isotropic in one inertial frame implies anisotropic shifts in others. Using observer Lorentz covariance, we derive the time-dependent variations in the relative resonance frequencies of a pair of electromagnetic resonators that would be generated by such a shift in the rest frame of the Sun. A new analysis of a recent experimental test of relativity using this result constrains $\tilde{\kappa}_{tr}$ with a precision of $7.4\times10^{-9}$. This represents the first constraint on $\tilde{\kappa}_{tr}$ by a Michelson-Morley experiment and the first analysis of a single experiment to simultaneously set limits on all nine non-birefringent terms in the photon sector of the SME.

A New Method for Robust Damping and Tracking Control of Scanning Probe Microscope Positioning Stages

This paper demonstrates a simple second-order controller that eliminates scan-induced oscillation and provides integral tracking action. The controller can be retrofitted to any scanning probe microscope with position sensors by implementing a simple digital controller or operational amplifier circuit. The controller is demonstrated to improve the tracking bandwidth of an NT-MDT scanning probe microscope from 15 Hz (with an integral controller) to 490 Hz while simultaneously improving gain-margin from 2 to 7 dB. The penalty on sensor induced positioning noise is minimal. A unique benefit of the proposed control scheme is the performance and stability robustness with respect to variations in resonance frequency. This is demonstrated experimentally by a change in resonance frequency from 934 to 140 Hz. This change does not compromise stability or significantly degrade performance. For the scanning probe microscope considered in this paper, the noise is marginally increased from 0.30 to 0.39 nm rms. Open and closed-loop experimental images of a calibration standard are reported at speeds of 1, 10, and 31 lines per second (with a scanner resonance frequency of 290 Hz). Compared with traditional integral controllers, the proposed controller provides a bandwidth improvement of greater than 10 times. This allows faster imaging and less tracking lag at low speeds.

Determination of Resonance Frequencies of Meander Line Antennas Using Two Dimensional Transmission Line Modeling Method

Small antennas are widely used in devices for consumer electronics. The dipole antenna is an example. However, dipole antennas, when decreasing the length, suffer serious drawbacks. Meander line antennas are used as a solution to reduce the resonance frequency of dipole antennas. In this paper, the resonance frequencies of meander line antennas were computed. Variation of resonance frequency with number of iterations and with arm length was investigated. All computations were carried out using a specially developed simulation program written in MATLAB. The program was based upon two-dimensional transmission line modeling method.

P‐174: Piezoelectric Tuning Technology to Compensate for Variation in Resonant Frequency in a MEMS Mirror

AbstractAn effective method to tune the resonant frequency of a micro scanning mirror with a piezoelectric element is presented. Though the resonant frequency (fr) is determined by the structure and size of the micromirror and the torsion bar, the fr varies according to the environmental temperature, driving voltage, and fatigue of the torsion beams. We have developed an effective mechanism to control the stress of the torsion bars using the piezoelectric elements and we succeeded in tuning 0.9% of the resonant frequency of the scanning mirror which corresponds to the variation of the emvironmental temperature with 83 degree.

The high frequency magnetic properties of self assembled Fe–Co–Si–N nanogranular thin films

The effect of a variation in Si and N concentration on the microstructure, crystal structure and high-frequency magnetic properties of Fe-Co-Si-N nanogranular thin films was investigated. The films, prepared by rf magnetron sput- tering, consisted of nanosized grains of FeCo as well as a Si and N rich intergranular amorphous phase. The Si con- centration had a significant effect on the crystal structure of the FeCo phase. The resistivities of the Fe-Co-Si-N films were significantly enhanced by an increase in Si concen- tration. The resonant frequency of the Fe-Co-Si-N films could be tuned from 0.45 GHz to 2.1 GHz by controlling Si concentration. The N concentration greatly influenced mag- netic properties and the variation in resonant frequency is in agreement with Kittel's equation.

Observation of an anomalous mass effect in microcantilever-based biosensing caused by adsorbed DNA

Quantifying adsorbed mass using resonance frequency variation in a microcantilever is an established technique. However, when applied to adsorbed mass determination in liquids, the resonance frequency variations represent several contributions. While the discrepancy between the apparent and real adsorbed mass is negligible for measurements in air, it can be significant in liquids. Here we present an anomalous effect of adsorbed DNA on the resonance frequency of microcantilevers which cannot be explained using current models. Our findings suggest that the measured frequency shifts may be explained on the basis of a hydrodynamic interaction caused by the adsorbed molecules on the cantilever.

Origin and reduction of motion and f0 artifacts in high resolution T2*-weighted magnetic resonance imaging: Application in Alzheimer's disease patients

The altered iron concentration in many neurodegenerative diseases such as Alzheimer's disease (AD) has led to the development of MRI sequences that are sensitive to the accompanying changes in the transverse relaxation rate. Heavily T2*-weighted imaging sequences at high magnetic field strength (7T and above), in particular, show potential for detecting small changes in iron concentration. However, these sequences require a long echo time in combination with a long scanning time for high resolution and are therefore prone to image artifacts caused by physiological fluctuations, patient motion or system instabilities. Many groups have found that the high image quality that was obtained using high resolution T2*-weighted sequences at 7T in healthy volunteers, could not be obtained in AD patients. In this study the source of the image artifacts was investigated in phantom and in healthy volunteer experiments by incorporating movement parameters and resonance frequency (f0) variations which were measured in AD patients. It was found that image degradation caused by typical f0 variations was a factor-of-four times larger than artifacts caused by movement characteristic of AD patients in the scanner. In addition to respiratory induced f0 variations, large jumps in the f0 were observed in AD patients. By implementing a navigator echo technique to correct for f0 variations, the image quality of high resolution T2*-weighted images increased considerably. This technique was successfully applied in five AD patients and in five subjective memory complainers. Visual scoring showed improvements in image quality in 9 out of 10 subjects. Ghosting levels were reduced by 24±13%.

Microwave Dielectric Properties of (Mg0.95Ni0.05)TiO3–SrTiO3 Ceramics with a Near‐Zero Temperature Coefficient of Resonant Frequency

The microwave dielectric properties of a (1−x)(Mg0.95Ni0.05)TiO3–xSrTiO3 ceramics system were investigated. The system was prepared using a conventional solid‐state ceramic method. To produce a temperature‐stable material, SrTiO3 was added, which led to a near‐zero temperature variation in resonant frequency. The variation in microwave dielectric properties of the (1−x)(Mg0.95Ni0.05)TiO3–xSrTiO3 ceramics system significantly depends on the amount of SrTiO3 present. As x was varied from 0.01 to 0.1, the microwave Q×f value decreased from 105,000 to 31,000 GHz and the dielectric constant (ɛr) increased from 18.74 to 26.5. A microwave dielectric material with a dielectric constant (ɛr) of 21, a Q×f value of 73,000 GHz, and a τf value of 1 ppm/°C were obtained from the compound 0.96(Mg0.95Ni0.05)TiO3–0.04SrTiO3 sintered at 1300°C for 4 h. To verify the performance of the 0.96(Mg0.95Ni0.05)TiO3–0.04SrTiO3 ceramics, a band‐pass filter with traditional hairpin resonators was designed and simulated on different dielectric materials [such as FR4, alumina, and 0.96(Mg0.95Ni0.05)TiO3–0.04SrTiO3].