Increase In Resonance Frequency Research Articles

LED-TV用 전원장치에 적합한 자동 권선형 고주파 공통 모드 초크의 특성 해석에 관한 연구

This paper presents the high frequency common mode (HFCM) choke with the winding method of automatic type capable of EMI attenuation of high frequency band / used in the EMI filter of LED-TV SMPS without PFC block. The high frequency common mode choke with the winding method of automatic type proposed in this paper can not only reduce the parasitic capacitance(Cp), but also ensure the uniformity of electrical characteristics by adopting the winding methods of multi-section bobbin and automatic types, compared to the conventional high frequency common mode choke with the winding method of manual type. The first resonant frequency of the proposed CM choke tends to increase as the parasitic capacitance becomes small and its impedance characteristics improved performance as the first resonant frequency increases, especially in the high frequency bands. The high frequency common mode choke (Cp) with the winding method of automatic type proposed in this paper shows that in the future, the method may have practical use in LED/OLED-TV SMPS and in several applications, such as LED Lighting, Laptop Adapter, and so on.

An experimental parametric study on natural circulation BWRs stability

A parametric study on the stability performance of a prototypical natural circulation BWR is performed with the downscaled GENESIS facility. The GENESIS design is based on fluid-to-fluid modeling and includes an artificial void reactivity feedback (VRF) system for simulating the neutronic-thermal-hydraulic coupling. In this work a more sophisticated VRF system than its predecessors is developed and implemented. The VRF allowed investigating different configurations relevant for the reactor design. The experiments show that changing the fuel rods diameter to a half (doubling) decreases (increases) the stability performance of the system while the resonance frequency increases (decreases). In addition, it is found that the use of MOX fuels in a BWR slightly decreases the stability performance of the reactor. On top of this, it is clearly observed that at least two oscillatory modes exists in the system, the thermal-hydraulic mode (associated to density waves traveling thorough the core plus chimney section) and the so-called reactor mode (related to density waves travelling thorough the core). It is observed that the last one is amplified by increasing (in an absolute sense) the void reactivity feedback coefficient. Details regarding the interplay between these oscillatory modes is also given.

Nonlinear analysis of a two-degree-of-freedom vibration energy harvester using high order spectral analysis techniques

Conventional vibration energy harvesters are generally based on linear mass-spring oscillator models. Major limitations with common designs are their narrow bandwidths and the increase of resonant frequency as the device is scaled down. To overcome these problems, a two-degree-of-freedom nonlinear velocity-amplified energy harvester has been developed. The device comprises two masses, oscillating one inside the other, between four sets of nonlinear magnetic springs. Impacts between the masses allow momentum transfer from the heavier mass to the lighter, providing velocity amplification. This paper studies the nonlinear effects introduced by the presence of magnetic springs, using high order spectral analysis techniques on experimental and simulated data obtained for a range of excitation levels and magnetic spring configurations, which enabled the effective spring constant to be varied. Standard power spectrum analysis only provide limited information on the response of nonlinear systems. Instead, bispectral analysis is used here to provide deeper insight of the complex dynamics of the nonlinear velocity-amplified energy harvester. The analysis allows identification of period-doubling and couplings between modes that could be used to choose geometrical parameters to enhance the bandwidth of the device.

Large scale integration of CVD-graphene based NEMS with narrow distribution of resonance parameters

We present a novel method for the fabrication of the arrays of suspended micron-sized membranes, based on monolayer pulsed-CVD graphene. Such devices are the source of an efficient integration of graphene nano-electro-mechanical resonators, compatible with production at the wafer scale using standard photolithography and processing tools. As the graphene surface is continuously protected by the same polymer layer during the whole process, suspended graphene membranes are clean and free of imperfections such as deposits, wrinkles and tears. Batch fabrication of 100 μm-long multi-connected suspended ribbons is presented. At room temperature, mechanical resonance of electrostatically-actuated devices show narrow distribution of their characteristic parameters with high quality factor and low effective mass and resonance frequencies, as expected for low stress and adsorbate-free membranes. Upon cooling, a sharp increase of both resonant frequency and quality factor is observed, enabling to extract the thermal expansion coefficient of CVD graphene. Comparison with state-of-the-art graphene NEMS is presented.

音響管粉粒体レベルスイッチ

This paper describes a new type of level switch which detects the existence of light, hot particulates such as ash in a tank. Here we employed an acoustic tube method. A port of the tube was driven by a piezo-sounder at less than its resonance frequency and the length L of the tube was selected to have the same resonance frequency, i.e., L=n×(half of the wave length). If the other port is covered by particulates, the acoustic impedance at the resonance frequency increases, which yields increases of the electric impedance of the piezo device. The sound velocity increases in proportion to the temperature, which may deteriorate the optimal measurement condition, i.e., the length of tube is not optimal at the altered temperature. However theoretical studies showed that covering a detected port by particulates mostly influenced the acoustic viscosity which is less influenced by the temperature change. As a result of theoretical studies, we showed that the proposed method can work in a certain temperature range. We verified the theoretical results using experiments which showed that the proposed method worked in the temperature range from 5°C to 80°C with a piezo sounder with 760 resonance frequency and an acoustic tube with half the wave length. Moreover, it detected particles with low bulk density such as those with 13kg/m3. We also conducted an experiment to judge the existence of gravel heated to 450°C in at a room temperature of 23°C which was successful.

Experimental investigation of frequency characteristics of the multistage slot membranes waveguide filters

In this article, we present results of experimental investigation of amplitude-frequency characteristics (AFC) of the five-stage “filters with the waveguide-slot membranes” (FWSM) in the range of frequencies 5.4…8.5 GHz for six filters. Article shows the following trend change filter frequency response by increasing the width of the slots of the second and fourth membranes: decrease the quality factor, resonant frequency increase, reducing losses in the passband.

Novel QCM-based Method to Predict in Vivo Behaviour of Nanoparticles

In biological fluids, proteins and other biomolecules bind to the surface of nanoparticles to form a coating known as the protein corona which in turn becomes primary determinant of the nanoparticles’ fate and behaviour. Here we develop a QCM-based platform and methodology to obtain data from real-time interactions of nanoparticles with selected human plasma proteins. Polystyrene particles coated with transferrin are immobilized on QCM sensor chips and by means of a ‘sandwich’ format binding assay, specific epitopes on the particles can be quantified as measured by the increase of the sensor's resonant frequency. Cell binding experiments where adherent cells are directly grown on the sensor surface are also performed. Interaction of nanoparticles injected over the cell surface is observed only in the case of particle-transferrin complexes demonstrating that it is the nanoparticle-corona complex, rather than the native nanoparticle, “what the cell sees”, with the corona being the interface between the nanoparticle and the cellular system. Our data highlight the potential of the proposed QCM-based platform and methodology for characterization of the bio-nano-interface and tracking the interaction of nanoparticles with biological cells in the presence of a realistic milieu.

Dynamic Buckling of Embedded Laminated Nanocomposite Plates Based on Sinusoidal Shear Deformation Theory

In this study, the dynamic buckling of the embedded laminated nanocomposite plates is investigated. The plates are reinforced with the single-walled carbon nanotubes (SWCNTs), and the Mori-Tanaka model is applied to obtain the equivalent material properties of them. Based on the sinusoidal shear deformation theory (SSDT), the motion equations are derived using the energy method and Hamilton's principle. The Navier’s method is used in conjunction with the Bolotin's method for obtaining the dynamic instability region (DIR) of the structure. The effects of different parameters such as the volume percentage of SWCNTs, the number and orientation angle of the layers, the elastic medium, and the geometrical parameters of the plates are shown on DIR of the structure. Results indicate that by increasing the volume percentage of SWCNTs the resonance frequency increases, and DIR shifts to right. Moreover, it is found that the present results are in good agreement with the previous researches.

How sensitive are site effects and building response to extreme cold temperature? The case of the Grenoble’s (France) City Hall building

In this paper, a simple analysis is done to explain the observed increase of resonance frequency of City-Hall building in Grenoble (France), a 12-story reinforced concrete building. This period corresponds also to the observed variation of the resonance frequency of the Grenoble’s sedimentary basin. The postulated hypothesis is that the frequency increase reflects the stiffness increase of the soil–structure system related to the cold period that hit Western Europe in 2012. To explore this hypothesis we have processed continuous recording during the early 2012 recorded at the roof level and at a close free-field accelerometric station. The variation of site effect is monitored by the horizontal-to-vertical spectral ratio of seismic noise, and the variation of apparent and system frequencies of the building by the random decrement technique. Apparent frequency is computed by deconvolution method between roof and basement. The maximum freezing penetration is 0.75 m and the horizontal relative motion stiffness of the foundation is strongly sensitive to the modification of the upper soil layer. The results suggest a variation (<1 %) larger than twice the standard deviation of the natural wandering of resonance frequency observed at City-Hall building for normal weather conditions, and question on the development of realistic models developed for the detection of damage and for the physical interpretation of such frequency variations observed in actual buildings.

Static and dynamic responses of a microcantilever with a T-shaped tip mass to an electrostatic actuation

In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The electrostatic force is generated by applying an electric voltage between the horizontal part of T-shaped tip mass and an opposite electrode plate. The cantilever microbeam is modeled as an Euler–Bernoulli beam. The T-shaped tip mass is assumed to be a rigid body and the nonlinear effect of electrostatic force is considered. An equation of motion and its associated boundary conditions are derived by the aid of combining the Hamilton principle and Newton’s method. An exact solution is obtained for static deflection and mode shape of vibration around the static position. The differential equation of nonlinear vibration around the static position is discretized using the Galerkin method. The system mode shapes are used as its related comparison functions. The discretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. In addition, effects of mass inertia, mass moment of inertia as well as rotation of the T-shaped mass, which were ignored in previous works, are considered in the analysis. It is shown that by increasing the length of the horizontal part of the T-shaped mass, the amount of static deflection increases, natural frequency decreases and nonlinear shift of the resonance frequency increases. It is concluded that attaching an electrode plate with a T-shaped configuration to the end of the cantilever microbeam results in a configuration with larger pull-in voltage and smaller nonlinear shift of the resonance frequency compared to the configuration in which the electrode plate is directly attached to it.

The microstructure, dielectric abnormalities, polar order and microwave dielectric properties of Ag(Nb1−xTax)O3 (x = 0–0.8) ceramics

Ag(Nb1−xTax)O3 (x=0–0.8) ceramics were prepared using a solid-state reaction method, and a single-phase perovskite was identified using XRD for dense ceramics with x=0–0.65. However, small Ag precipitates and microstructural inhomogeneities were observed using BSE-SEM and EDS. There are four kinds of dielectric abnormalities at RF frequencies, including a new abnormality that has a strong relaxation in the dielectric loss. A ferrielectric-like dielectric tunability was observed at 20–80°C for x=0 and 0.2, while the ceramic with x=0.5 exhibited an antiferroelectric-like dielectric tunability. Furthermore, a transition behaviour was observed for x=0.35, indicating that the ferrielectric–antiferroelectric transition does not correspond to the M1–M2 phase transition. The microwave dielectric constant of Ag(Nb1−xTax)O3 ceramics reaches its maximum value at x=0.35, while the Qf value and the temperature coefficient of resonant frequency increase monotonously with the value of x.

Transient potassium channels augment degeneracy in hippocampal active dendritic spectral tuning.

Hippocampal pyramidal neurons express an intraneuronal map of spectral tuning mediated by hyperpolarization-activated cyclic-nucleotide-gated nonspecific-cation channels. Modeling studies have predicted a critical regulatory role for A-type potassium (KA) channels towards augmenting functional robustness of this map. To test this, we performed patch-clamp recordings from soma and dendrites of rat hippocampal pyramidal neurons, and measured spectral tuning before and after blocking KA channels using two structurally distinct pharmacological agents. Consistent with computational predictions, we found that blocking KA channels resulted in a significant reduction in resonance frequency and significant increases in input resistance, impedance amplitude and action-potential firing frequency across the somato-apical trunk. Furthermore, across all measured locations, blocking KA channels enhanced temporal summation of postsynaptic potentials and critically altered the impedance phase profile, resulting in a significant reduction in total inductive phase. Finally, pair-wise correlations between intraneuronal percentage changes (after blocking KA channels) in different measurements were mostly weak, suggesting differential regulation of different physiological properties by KA channels. Our results unveil a pivotal role for fast transient channels in regulating theta-frequency spectral tuning and intrinsic phase response, and suggest that degeneracy with reference to several coexisting functional maps is mediated by cross-channel interactions across the active dendritic arbor.

Vibrational and acoustic responses of a laminated plate with temperature gradient along the thickness

Analytical study is carried out on the dynamic characteristics of a laminated plate under temperature gradient. Theoretical formulations are derived with the first order shear deformation theory and von Karman nonlinear strain displacement relationship considering the effect of temperature gradient. Semi-analytical solutions of vibration and acoustic responses are obtained for different temperature gradients. The correctness of the theoretical method is demonstrated by comparing with the experimental result and numerical simulation. The present work theoretically explains why the lowest point (buckling occurring) of the experimental curve of resonant frequencies for thermal structure is shifting up away from the horizontal axis. It also means that initial thermal deformation and thermal stress have to be considered together in simulation of the dynamical response for thermal structure. Research results show that with increasing temperature gradients, the resonant frequency increases, the critical mid-plane temperature at which resonant frequency drops to the lowest decreases, and the response peaks move toward higher frequency.

Dependence of Current and Magnetic Field on Spin Transfer Induced Noise in CPP-GMR read Heads

This paper aims to investigate the magnetic noise dependence on the sense current, Isense, and the hard bias field, HB, of the current perpendicular to the plane giant magnetoresistance read heads. The macrospin modeling was performed in the simulations. The magnetic noise was examined by using power spectral density analysis. The results showed that the magnetic noise was increased with increasing Isense due to an enhancement of STT effect, especially a rapid increase of the noise was found when Isense exceeds a critical value. An asymmetry of Isense indicated that a negative current produces lower noise than a positive current since a ferromagnetic exchange coupling was existed in the model. In addition, the noise could be reduced by increasing HB which further results in an increase of the ferromagnetic resonance frequency. Hence, an optimization of Isense and HB strongly influences the magnetic noise and becomes an important factor for acheiving the high performance magnetic read head for higher recording densities.

Effects of occupant weight and sitting posture on vehicle seat structural dynamics

The characterisation of the occupied vehicle seat structural dynamics is still challenging owing to the complex and nonlinear dynamic behaviour of the human body. The human body has significant influences on the occupied vehicle seat structural dynamics. In this paper, the structural dynamics of the unoccupied seat, occupied seat in lean-on posture, and occupied seat in lean-off posture are investigated. The results of this investigation show that, in lean-on condition when the occupant weight increases, the lateral resonant frequencies of the seat decrease whereas both fore-aft resonant frequency and twisting resonant frequency increase. The structural resonant frequencies of the occupied seat in lean-off condition are considerably different from those in the corresponding lean-on condition. This indicates that the coupling of the occupant body and the seatback plays a major role on occupied seat structural dynamics and transmission of the vibration to the occupant body in frequencies where the seat has structural vibration modes.

On-chip preparation of nanoscale contrast agents towards high-resolution ultrasound imaging.

Micron-sized lipid-stabilised bubbles of heavy gas have been utilised as contrast agents for diagnostic ultrasound (US) imaging for many years. Typically bubbles between 1 and 8 μm in diameter are produced to enhance imaging in US by scattering sound waves more efficiently than surrounding tissue. A potential area of interest for Contrast Enhanced Ultrasound (CEUS) are bubbles with diameters <1 μm or 'nanobubbles.' As bubble diameter decreases, ultrasonic resonant frequency increases, which could lead to an improvement in resolution for high-frequency imaging applications when using nanobubbles. In addition, current US contrast agents are limited by their size to the vasculature in vivo. However, molecular-targeted nanobubbles could penetrate into the extra-vascular space of cancerous tissue providing contrast in regions inaccessible to traditional microbubbles. This paper reports a new microfluidic method for the generation of sub-micron sized lipid stabilised particles containing perfluorocarbon (PFC). The nanoparticles are produced in a unique atomisation-like flow regime at high production rates, in excess of 10(6) particles per s and at high concentration, typically >10(11) particles per mL. The average particle diameter appears to be around 100-200 nm. These particles, suspected of being a mix of liquid and gaseous C4F10 due to Laplace pressure, then phase convert into nanometer sized bubbles on the application of US. In vitro ultrasound characterisation from these nanoparticle populations showed strong backscattering compared to aqueous filled liposomes of a similar size. The nanoparticles were stable upon injection and gave excellent contrast enhancement when used for in vivo imaging, compared to microbubbles with an equivalent shell composition.

Interaction of an ultrasound-activated contrast microbubble with a wall at arbitrary separation distances

Both in vitro and in vivo, contrast agent microbubbles move near bounding surfaces, such as the wall of an experimental container or the wall of a blood vessel. This problem inspires interest in theoretical models that predict the effect of a wall on the dynamics of a contrast microbubble. There are models for a bubble at a large distance from a wall and for a bubble adherent to a wall. The aim of the present study is to develop a generalized model that describes the dynamics of a contrast microbubble at arbitrary distances from a wall and thereby make it possible to simulate the acoustic response of the bubble starting from large separation distances up to contact between the bubble and the wall. The wall is assumed to be a plane. Therefore, the developed model applies for in vitro investigations of contrast agents in experimental containers. It can also be used as a first approximation to the case of a contrast microbubble within a large blood vessel. The derivation of the model is based on the multipole expansion of the bubble velocity potential, the image source method, and the Lagrangian formalism. The model consists of two coupled equations, one of which describes the bubble radial oscillation and the second describes the translation of the bubble center. Numerical simulations are performed to determine how the acoustic response of a contrast microbubble depends on the separation distance near walls of different types: rigid, plastic, arterial, etc. The dynamics of the bubble encapsulation is described by the Marmottant shell model. The properties of the plastic wall correspond to OptiCell chambers commonly used in experiments. The results of the simulations show that the bubble resonance frequency near a wall depends on both the separation distance and the wall material properties. In particular, the rigid wall makes the resonance frequency decrease with decreasing separation distance, whereas in the vicinity of the OptiCell wall and the arterial wall, the resonance frequency increases. The theoretical model is validated by comparing with experimental data available in the literature for phospholipid-shelled microbubbles near a compliant agarose gel boundary. The comparison is conducted for two data sets. In the first case, the simulated and measured parameters of the bubble acoustic response (resonance frequency and maximum amplitude of the scattered pressure) are compared as a function of bubble diameter, using the experimental data obtained for bubbles with diameters ranging from 2.3 to 4 μm, insonified at 30 kPa in the frequency range from 4 to 13.5 MHz. In the second case, the simulated and measured values of the maximum amplitude of the scattered pressure are compared as a function of separation distance from the agarose boundary, using the experimental data for a 2.3 μm-diameter bubble insonicated at 69 kPa and 11 MHz. In both cases, the theoretical model correctly predicts the qualitative tendency in the behavior of the measured quantities and their quantitative level.

Size-dependent magnetization dynamics in individual Ni80Fe20 disk using micro-focused Brillouin Light Scattering spectroscopy

A direct and systematic investigation of the magnetization dynamics in individual circular Ni80Fe20 disk of diameter (D) in the range from 300 nm to 1 μm measured using micro-focused Brillouin Light Scattering (μ-BLS) spectroscopy is presented. At high field, when the disks are in a single domain state, the resonance frequency of the uniform center mode is observed to reduce with reducing disk’s diameter. For D = 300 nm, additional edge and end-domains resonant modes are observed due to size effects. At low field, when the disks are in a vortex state, a systematic increase of resonant frequency of magnetostatic modes in a vortex state with the square root of the disks’ aspect ratio (thickness divided by radius) is observed. Such dependence diminishes for disks with larger aspect ratio due to an increasing exchange energy contribution. Micromagnetic simulations are in excellent agreement with the experiments.

Softening of stressed granular packings with resonant sound waves.

We perform numerical simulations of a two-dimensional bidisperse granular packing subjected to both a static confining pressure and a sinusoidal dynamic forcing applied by a wall on one edge of the packing. We measure the response experienced by a wall on the opposite edge of the packing and obtain the resonant frequency of the packing as the static or dynamic pressures are varied. Under increasing static pressure, the resonant frequency increases, indicating a velocity increase of elastic waves propagating through the packing. In contrast, when the dynamic amplitude is increased for fixed static pressure, the resonant frequency decreases, indicating a decrease in the wave velocity. This occurs both for compressional and for shear dynamic forcing and is in agreement with experimental results. We find that the average contact number Zc at the resonant frequency decreases with increasing dynamic amplitude, indicating that the elastic softening of the packing is associated with a reduced number of grain-grain contacts through which the elastic waves can travel. We image the excitations created in the packing and show that there are localized disturbances or soft spots that become more prevalent with increasing dynamic amplitude. Our results are in agreement with experiments on glass bead packings and earth materials such as sandstone and granite and may be relevant to the decrease in elastic wave velocities that has been observed to occur near fault zones after strong earthquakes, in surficial sediments during strong ground motion, and in structures during earthquake excitation.

Sr(Ga0.5Nb0.5)1−xTixO3 Low‐Loss Microwave Dielectric Ceramics with Medium Dielectric Constant

The microwave dielectric properties of Sr(Ga0.5Nb0.5)1−xTixO3 (x = 0, 0.1, 0.2 and 0.3) ceramics have been investigated together with their microstructures. Single‐phase solid solutions are achieved in this series of ceramics. The ordering features are comprehensively analyzed by transmission electron microscopy and Raman spectroscopy. Local 1:1 ordering in B‐site leads to a double‐cubic structure with space group , while Ti substitution disrupts this 1:1 ordering between Ga and Nb, and the metastable ordering between Ti and (Ga + Nb) is speculated to form due to their large size difference. The dielectric constant and temperature coefficient of resonant frequency increase nonlinearly as x increases, while the Qf value decreases gradually. The variation trend of Qf value is mainly attributed to the intrinsic loss because of the increasing vibrational anharmonicity by Ti substitution. The ordering transition from short coherence, long‐range ordering to short‐range ordering with increasing Ti content has an agreeable and weak effect on the Qf value. The best combination of microwave dielectric properties is achieved for the composition of x = 0.3: εr = 46.6, Qf = 42 200 GHz and τf = 5.0 ppm/°C.