Change In Q-factor Research Articles

Effects of Small and Normalized Q-Factor Changes and Knee Alignment on Knee Biomechanics during Stationary Cycling.

Increasing inter-pedal distance (Q-Factor: QF) in cycling increases peak internal knee abduction moments (KAbM). The effect of smaller and normalized changes in QF has not been investigated. The purposes of this study were to examine changes in KAbM with small and normalized increases and whether static knee alignment accounts for any changes in knee biomechanics in cycling. Fifteen healthy participants were included (age: 22.7 ± 2.5 years, BMI: 23.95 ± 3.21 kg/m2). Motion capture and instrumented pedals collected kinematic and pedal reaction force (PRF) data, respectively, while participants cycled at five different QFs. Each participant's mechanical axis angle (MAA) was estimated using motion capture. Each participant's QFs were normalized by starting at 160 mm and increasing by 2% of the participant's leg length (L), where the five QF conditions were as follows: QF1 (160), QF2 (160 + 0.02 × L), QF3 (160 + 0.04 × L), QF4 (160 + 0.06 × L), and QF5 (160 + 0.08 × L). A linear mixed model was performed to detect differences between QF conditions. KAbM increased by more than 30% in QF5 from QF1, QF2, QF3, and QF4. Medial PRF increased by at least 20% in QF5 from QF1, QF2, and QF3. MAA had varying degrees of correlation with the variables of interest. These results suggest that KAbM is more sensitive to changes in QF at greater QF increases.

Development of long-range conductivity mechanisms in glass-like carbon

The conductivity mechanisms in glass-like carbon synthesised from SU-8 3005 photoresist are explored as a function of pyrolysis temperature (between 700–750 °C) utilising microwave dielectric spectroscopy techniques. Broadband measurements using an open-ended coaxial probe (BCP) are used to investigate the complex permittivity and conductivity as a function of frequency and show the development of long range conduction and sp2 carbon chain formation. Fixed frequency resonance measurements using microwave cavity perturbation (MCP) methods are shown as a way of measuring this transition and change in Q-factor without requiring contacts and therefore acting as a effective method for non-destructive and non-invasive measurements. Using these methods we show a clear change in the AC conductivity of glass-like carbon at a pyrolysis temperature of ∼730 °C and demonstrate how microwave cavity perturbation (MCP) can be used as a non-contact method of dielectric spectroscopy for determining the transition of conductivity mechanisms in glass-like carbon from short to long range and therefore as a method for non-destructive material quality control. We demonstrate that both BCP and MCP dielectric spectroscopy methods are effective at clearly detecting changes in the structure and conductivity mechanisms of glass-like carbon over a small pyrolysis temperature range.

Microwave acoustic studies of materials in diamond anvil cell under high pressure

This paper presents an integrated measuring system combining a diamond anvil cell (DAC) and a high overtone bulk acoustic resonator (HBAR) operating at the microwave frequency band as 2.8–8.8 GHz. We have studied several metallic (W, Zr) and semiconductor (Si) samples under pressure up to ∼16 GPa. As an HBAR, we have used the “Al/Al0.72Sc0.28N/Mo/(100) diamond” structure utilizing a piezoelectric aluminum–scandium nitride film. We have observed that under pressure, the Q-factor of the HBAR decreases but remains at the value of 2500–3000, which is suitable for our experiments. It is demonstrated that the above system can be used for studying the behavior of various solids under high pressure, the pressure-induced phase transition in Zr, the registration of plastic deformations, and their relaxation in metals. Here, we discussed the phenomenon of an acoustic wave passing through a tungsten layer under a pressure of ∼5.5 GPa. The integrated DAC&HBAR measuring system has demonstrated some practical advantages over known ultrasonic systems combined with the DAC as the possibility of applying a microwave operational frequency, the measurement of a Q-factor change under pressure, and the miniature size of a sensitive HBAR element. The application of the built-in DAC&HBAR system will hopefully allow more accurate studies on materials in the GPa pressure range of a DAC.

Triple Mass Resonator for Electrostatic Quality Factor Tuning

In this paper, a triple mass resonator (TMR) with a high capability to independently tune both resonant frequency and quality factor (Q-factor) is reported. An additive oscillating structure is designed into a conventional dual-mass resonator to control the modal shape. The theoretical studies revealed that the amplitude ratio between the outer masses, which mainly determine the Q-factor through the anchor loss, is sensitive to both suspension and inner springs because of mode coupling, while the resonant frequency is only sensitive to the suspension spring. Through this mechanism, the quality factor related to the anchor loss, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q_{\mathrm {Anchor}}$ </tex-math></inline-formula> , can be adjusted by electrostatic tuning of the inner spring, while the resonant frequency keeps almost constant. On the other hand, the eigenfrequency could be significantly tuned by the electrostatic tuning of the suspension spring. The experimental results showed the Q-factor could be tuned as large as 19% by a DC bias of 15 V at the inner electrode, while the resonant frequency change was only as small as 162 ppm. In contrast, when the DC bias was applied to soften the suspension stiffness, the resonant frequency could be tuned as high as 7023 ppm with Q-factor change of 16%. [2021-0167]

Resonance-enhanced spectral funneling in Fabry–Perot resonators with a temporal boundary mirror

Abstract A temporal boundary refers to a specific time at which the properties of an optical medium are abruptly changed. When light interacts with the temporal boundary, its spectral content can be redistributed due to the breaking of continuous time-translational symmetry of the medium where light resides. In this work, we use this principle to demonstrate, at terahertz (THz) frequencies, the resonance-enhanced spectral funneling of light coupled to a Fabry–Perot resonator with a temporal boundary mirror. To produce a temporal boundary effect, we abruptly increase the reflectance of a mirror constituting the Fabry–Perot resonator and, correspondingly, its quality factor in a step-like manner. The abrupt increase in the mirror reflectance leads to a trimming of the coupled THz pulse that causes the pulse to broaden in the spectral domain. Through this dynamic resonant process, the spectral contents of the input THz pulse are redistributed into the modal frequencies of the high-Q Fabry–Perot resonator formed after the temporal boundary. An energy conversion efficiency of up to 33% was recorded for funneling into the fundamental mode with a Fabry–Perot resonator exhibiting a sudden Q-factor change from 4.8 to 48. We anticipate that the proposed resonance-enhanced spectral funneling technique could be further utilized in the development of efficient mechanically tunable narrowband terahertz sources for diverse applications.

Comparative Study on Sensing Properties of Fiber-Coupled Microbottle Resonators With Polymer Materials

Optical whispering gallery mode (WGM) microbottle resonators based on a variety of polymer materials (benzocyclobutene (BCB), UV88 (Relentless, China) and Loctite3525 (HenKel, Germany)) were fabricated and investigated experimentally. The polymer materials were spin-coated onto the fiber and cured by ultraviolet (UV) light followed by heating to form a microbottle structure of different shapes and diameters. The WGMs were excited by tapered fiber, and the spectral characteristics of all realized microbottle cavities were evaluated, such as quality factor (Q > 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> ), free spectral range and polarization mode (TE and TM). The temperature and refractive index (RI) sensing performance are analyzed and Q-factor changes during the sensing process. In addition, a newly application of UV light intensity sensing for the polymer microbottle resonators was also demonstrated firstly. According to the experimental results that the microbottle resonator of BCB displays good UV light intensity sensitivity (0.0011 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nm</i> /( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mw/cm</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> )) and figure of merit (FOM) (0.0122/( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mw/cm</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> )). This sensor is a simple structure, low-cost material, robust performance, and possesses attractive application prospects in sensing and optical devices.

Dielectric replica measurement: a new technique for obtaining the complex permittivity of irregularly shaped objects

Dielectric measurements provide valuable information about the properties of materials, and could be used to classify and identify the source of objects in fields such as archaeology. Current methods of identification are all partly destructive, so an innovative electromagnetic method developed by the authors, based on resonant cavity perturbation (RCP), provides an attractive, non-destructive alternative. A problem with traditional RCP is that the changes in frequency and Q-factor vary with the object’s shape; however, we overcome this by creating a replica of the object, from a material whose dielectric properties are known. Then, by combining three separate perturbations with orthogonal field directions, due firstly to the object and then to its replica, we eliminate the shape dependency, and thus determine the object’s dielectric constant and loss factor. After developing the theory of this novel DRM technique, we demonstrate the principle using a set of geometric shapes made in both polytetrafluoroethylene and a 3D printed material. Further measurements then enable second-order terms to be included in the model, improving its accuracy. Finally, DRM is shown to be capable of distinguishing two irregularly shaped objects of different materials. Potential applications of DRM include determining the provenance of pottery, glasses and flints, and distinguishing ivory from bone. These would be of interest to customs and environmental agencies, as well as museum curators and archaeologists.

Design and Modeling of MEMS-Based Trace-Level Moisture Measurement System for GIS Applications in Smart Grid Environment

This paper presents a system to monitor the presence of trace moisture in SF6 gas insulated switchgear (GIS) employing a micro-cantilever sensor. The main objective of the proposed system design is to continuously monitor the moisture concentration inside the GIS for enhanced safety. Microcantilever-based sensors reduce the overall size of the measurement system as well as enhance the measurement accuracy and sensitivity. A new system approach is proposed to detect trace moisture by monitoring the change in Q-factor of the microcantilever. It makes the measurement of resonant frequency of the microcantilever easier to implement and analyze. The system is made Internet of Things (IoT) enabled using Raspberry Pi. It allows easy local and remote accessibility of sensor data. The usefulness of the proposed system lies in its continuous monitoring ability, compact nature, and easy integration and accessibility, which are some of the essential and current requirements of the smart grid environment.

Sensitivity Optimization of Microwave Biosensors

A microwave biosensor, suitable for the detection of dielectric overlays, formed by bonding of bio-molecules to a functionalized substrate, is investigated. The sensor consists of a resonant coupled split-ring configuration in microstrip technology. An analytical model for the sensor structure is developed and compared to measurement results. The complexity of the model is further reduced and equations for resonance frequency shift and Q-factor change are determined from which the sensitivity and the detection limit can be estimated. It is found that higher operating frequencies facilitate higher sensitivity and that the electrical conductivity of the sample dominates the Q-factors and therefore the achievable accuracy.

Geometrical Enhancement of Planar Loop Antennas for Inductive Near-Field Data Links

The low Q-factor requirements of High-Frequency Radio Frequency Identification (HF-RFID) interrogator antennas constrain transmission performance when they are used in data links requiring similar terminal antennas. This letter presents a geometrical approach to enhance the transmission performance of planar loop antennas without a significant change to their standalone performance as HF-RFID interrogator antennas. The method distributes the turns of a modified planar square loop antenna to enhance the coupling level in a symmetric link, while limiting the change in Q-factor from a conventional HF-RFID interrogator antenna. Results from a presented test case show that the design method enables a 5.75% increase in peak transmission coefficient, and a 28.42% fractional bandwidth increase in a symmetric link, compared to a conventional design.

A novel concept of acousto-optic ring frequency shifters on silicon-on-insulator technology

In this paper, a ring frequency shifter using surface acoustic waves (SAW) is developed on a silicon-on-insulator (SOI) technology, in which, a design is introduced to make SOI waveguide piezoelectric by putting ZnO on SOI layer. A simulation shows that the refractive index change of SOI waveguide with an overlayer of ZnO is about 10 −3 by SAW of 100 mW. A finite-difference time domain (FDTD) is used to model the new concept of a ring frequency shifter using SAW of 100 mW. The results show that the resonance wavelength of a ring resonator with a radius of 50 μm shifts 22.7% of a free spectral range (FSR) due to the refractive index change of waveguide by SAW without change in transmission on resonances and finesse, a tiny change in bandwidth, Q-factor and FSR of a ring resonator. • A novel concept of acousto-optic ring modulator on silicon-on-insulator technology is presented. • A design is introduced to make SOI waveguide piezoelectric by putting ZnO on SOI layer. • The resonance wavelength of the ring resonator with a radius of 50 μm shifts 22.7% of FSR by SAW modulation.

Analysis of Video Signal Transmission Through DWDM Network Based on a Quality Check Algorithm

This paper provides an analysis of the multiplexed video signal transmission through the Dense Wavelength Division Multiplexing (DWDM) network based on a quality check algorithm, which determines where the interruption of the transmission quality starts. On the basis of this algorithm, simulations of transmission for specific values of fiber parameters ​​ are executed. The analysis of the results shows how the BER and Q-factor change depends on the length of the fiber, i.e. on the number of amplifiers, and what kind of an effect the number of multiplexed channels and the flow rate per channel have on a transmited signals. Analysis of DWDM systems is performed in the software package OptiSystem 7.0, which is designed for systems with flow rates of 2.5 Gb/s and 10 Gb/s per channel.

Investigation of the Viscoelastic Properties of Liquids Trapped in Nanoporous Cavities using Micromachined Acoustic Transducers

We have designed and fabricated 60MHz bulk acoustic wave transducers and demonstrated the efficacy of these devices for probing the gravimetric and viscoelastic properties of layers in intimate contact with one of the electrodes. By integrating a 100nm thick nanoporous film as the top electrode of the quartz resonator, we have been able to obtain enhanced sensitivity to mass loading and investigate the physical properties of liquids confined within 25–35nm pores. By experimentally measuring the change in resonance frequency and Q-factor at the first and third resonance modes and using a detailed acoustic model in which the trapped liquid is treated as viscoelastic layer under a viscous liquid, the properties of trapped water-glycerol mixture confined in nanopores has been deduced.

Fabrication and performance characteristics of high-frequency micromachined bulk acoustic wave quartz resonator arrays

This paper reviews the fabrication and performance of micromachined quartz resonator arrays. Using inductively coupled plasma etching techniques, we have successfully fabricated micromachined quartz resonator arrays with fundamental frequencies in the range of 25–85 MHz in an array format. These resonators have been experimentally evaluated for their performance in viscous (liquid) and viscoelastic (a biomolecular film in liquid) loading conditions. The paper discusses the ultimate sensitivity to mass and other properties of the adsorbates/contacting materials onto high-frequency quartz resonator surfaces. Measuring the frequency and Q-factor changes at the fundamental and third overtone of a 66 MHz resonator upon adsorption of immunoglobulin G (IgG) protein film on a hexadecanethiol functionalized surface, we were able to deduce: (i) the film thickness = 18 nm, (ii) density = 1040 kg m−3, (iii) elastic modulus = 6.7 MPa and (iv) viscosity = 5.5 mPa s. Furthermore, from the adsorption isotherm for the IgG film, two different Langmuir equilibrium constants (K) were deduced. In the low-concentration region K = 2.13 × 108 M−1 and in the high-concentration region K = 6.53 × 106 M−1 were obtained. The thickness and density values obtained for IgG are consistent with the bilayer model predicted from interfacial packing of spherical protein molecules as a function of the molecular weight, and K values are consistent with earlier reported values for adsorption of IgG films. This is the first reporting of the elastic modulus and viscosity of IgG films in phosphate buffer solution.

Measurements of the complex permittivity and the complex permeability of low and medium loss isotropic and uniaxially anisotropic metamaterials at microwave frequencies

Split dielectric resonators operating in a quasi-TE011 mode were used for the measurement of the complex permittivity and the complex permeability of planar metamaterials deposited on low-loss dielectric substrates at microwave frequencies. Separation of the complex permittivity from the complex permeability for a specific metamaterial was achieved by performing measurements of the resonance frequencies and the Q-factors of a split post-dielectric resonator with two samples having different diameters but identical patterns. Measurements of the resonance frequencies and the Q-factors of empty substrates served as reference materials to determine the resonance frequency shifts and Q-factor changes due to the presence of the metamaterial only. The effective complex permittivity and permeability were determined on the basis of accurate electromagnetic modeling of the resonance structures containing the samples.

Characterization of viscoelastic properties of adsorbed biomolecules and biomolecular assemblies with high frequency micromachined quartz resonators

Micromachined quartz crystal resonator arrays operating in the 66–69 MHz fundamental mode range were tested for their ability to provide high sensitivity to mass loading and viscoelastic properties of biomolecules and biomolecular assemblies. Calibrations using viscous water–glycerol mixtures give the expected linear dependence on the square root of the density–viscosity product. Sequential adsorption of avidin layers interspersed with dithiobis(sulfosuccinimidylpropionate) (DTSSP) or biotynilated bovine albumin (BBA) cross-linker layers provided thick and planar viscoelastic layers for testing. The data reveal a high Q-factor sensitivity and the observed complex impedance changes could be accounted for using a layer dependent, variable viscosity model treated with continuum mechanics approach. The best interpretation of the frequency and Q-factor changes indicates that the layer material properties are most likely dominated by the frictional effects arising from the inter-linking molecules between the layers. These results show the ability of these high frequency micro resonators as an incisive tool for analyzing both static loading and dynamic viscoelastic properties of bimolecular adsorbates.

Proximity Effect in Quartz Crystal Microbalance

When an object approaches a vibrating quartz crystal microbalance (QCM) the resonant frequency changes. This "proximity effect" was seen at the distance of 10 mm in air and became more pronounced as the distance decreased. This effect depends on the quality factor (Q-factor) value of a QCM, conductivity of the object, and electrical connection of the object to QCM electrodes. A special setup was constructed to test the impact of the proximity effect on a QCM. Damping fluid was placed on one side of QCM, to change the Q-factor. A conducting metal disk was brought close to the other side of the QCM exposed to air. By varying the distance between the QCM and an object (metal disk), a shift in frequency was observed. This proximity effect was largest (>200 Hz for 10 MHz QCM) when the Q-factor was low and a conducting metal disk (e.g., Cu) was electrically shorted to the proximal (nearest) QCM electrode. The finite element modeling showed that the proximity effect was likely due to interaction of the object with the fringing electromagnetic field of the QCM. A simple modified Butterworth Van-Dyke model was used to describe this effect. It must be recognized that this effect may lead to large experimental artifacts in a variety of analytical QCM applications where the Q-factor changes. Therefore, in order to avoid artifacts, QCM and similar mass acoustic devices should not operate in the low Q-factor (<1000) regime.

COUPLING LASER POWER INTO A SLAB-SYMMETRIC ACCELERATOR STRUCTURE

We present a detailed analysis of the coupling of external laser fields into a resonant acceleration structure. The structure is slab-symmetric and consists of metal boundaries lined with dielectric; coupling is accomplished via an array of narrow, equally-spaced slots in the upper structure boundary. Effects of the couplers on the structure fields are investigated using both theory and 2-dimensional time-dependent simulation. Details of the resonance are found to be highly sensitive to the coupling slot geometry: the presence of the couplers can lead to frequency detuning, changes in the field breakdown limits and overall Q-factor, and distortions of the field pattern. Beam wakefields are enhanced by the presence of the slots, but found to have no significant effect on the beam transport. The resonant accelerating fields in this case are nearly constant along the short transverse direction and are found to have between 10 and 15 times the amplitude of the driving radiation.

Mode frequency shifts and Q-factor Changes in 2D microflower cavity and its deformed cavity

Mode frequency shifts and Q-factor changes in 2D microflower cavity and its deformed cavity are analyzed. The effective mode-splitting of double-degenerate WG modes is obtained and the Q-factor changes of matched and mismatched modes are discussed for the microflower cavity. The Q-factor stability of the splitted WGH (8,1) modes due to two types of local deformations is studied, showing that the local deformations can badly spoil the mode Q-factor if the deformations are not controlled properly. The output directionality of the splitted WGH (8,1) modes due to the local deformations also is presented, and a basically unidirectional light output of OO mode under local deformation DA (deformation happens at one “valley” of the microflower cavity) is obtained.

A combined Q and heterodyne sensor incorporating real-time DSP for reinforcement imaging, corrosion detection and material characterisation

An inductive sensor is described that is used to image steel reinforcement bars in concrete and to visualise surface corrosion. When a conductive target is placed within the vicinity of the sensing coil, an EMF is induced that opposes the change producing it. This causes a reduction in the Q-factor of the coil and a fall in amplitude of the excitation signal. When a non-conducting ferrous target such as corrosion product is present, a local increase in magnetic flux density occurs that in turn causes the inductance of the sensing coil to increase, reducing the resonant frequency of the tuned-system. The changes in Q-factor and resonant frequency are measured to image both the parent steel and surface corrosion. The circuit is designed to respond to very small changes in the received signal amplitude via a sensitive gain system, and to small changes in frequency, through the application of heterodyning. The excitation frequency has been selected so that the skin effect restricts the flow of eddy currents to the surface of the target. In this manner, surface features such as cracks and corrosion may be identified. The measured parameters are ultimately expressed as voltages before being applied to a purpose-designed DSP system. This averages signals in real-time, allowing high speed scanning. Feedback stabilisation is also applied between the DSP system and sensor to minimise voltage drift. At present it is possible to detect a steel bar to a depth of 200 mm and to image steel and surface corrosion to a depth 60 mm. Additionally, it is possible to image a range of materials for which non-destructive testing is important, such as graphite rods used in the nuclear industry. Since eddy currents are disrupted by vertical cracks, these features are readily detected by the system.