Oscillator Devices Research Articles

Experimental study on the periodic pulsating ventilation by fluidic oscillator on pollutant dispersion and ventilation performance in enclosed environment

Ventilation plays an essential role in creating healthy and comfortable indoor environment, while adopting unsteady airflow field has the potential to improve the indoor air mixing effect, which is conducive to the dispersion and eventually the discharge of indoor pollutants. A fluidic oscillator capable of producing periodic pulsating airflow is employed to conduct a ventilation experiment to test the performance of such unsteady flow regime. The distribution of indoor pollutants at different source locations is compared under both steady and unsteady ventilation mode. The assessment of the fluidic oscillator ventilation system performance in eliminating pollutants involves the concentration exceedance rate, the decay of indoor pollutant concentration, and the resultant ventilation efficiency. At a relatively lower air supply rate, the fluidic oscillator device can enhance indoor air mixing, leading to a reduction of the peak indoor pollutant concentration. Additionally, the fluidic oscillator air terminal significantly prolongs the time needed to reach the pollutant concentration threshold, increases ventilation efficiency, and improves indoor air quality.

A simplified drop breakage model for emulsion-producing fluidic devices: Application to fluidic oscillator, helical coil and vortex-based cavitation device

Droplet size distribution (DSD) is one of the key quality attributes of liquid–liquid emulsions. Various fluidic devices are used to generate emulsions. Most of the currently available models for estimating DSD are complicated to implement and computationally expensive. In this work, we have developed a simplified drop breakage model that is easy to implement and computationally inexpensive. This model approximates DSDs in three droplet populations, each characterised by a mean diameter. The developed drop breakage model was applied to simulate Sauter mean diameters of oil-in-water emulsions generated using three fluidic devices covering a broad range of shear rates and droplet sizes namely: vortex-based cavitation device (VD), helical coil (HC), and fluidic oscillator (FO). The variation of DSD with the number of passes (np) through the emulsion-producing fluidic devices was measured experimentally. The Sauter mean diameter (d32) and number of droplets (n) in each population were estimated from the measured DSD data. The procedure to estimate model parameters is presented. The simplified breakage model presented here was able to simulate the influence of the number of passes and operating conditions on Sauter mean diameter as well as breakage efficiency. VD was found to exhibit the highest drop breakage efficiency. FO was found to be a preferred choice for low (< 20 J/kg) energy consumption, HC for the middle range (20 – 100 J/kg) and VD for the higher (> 100 J/kg) range of energy consumption. The developed approach and model provide a simplified way of simulating the Sauter mean diameters of emulsions for a variety of emulsion-generating devices.

In vitro comparative study of wall portbased high-frequency chest wall oscillation device and internal air-pulse generator device.

Owing to environmental and disease issues, the use of high-frequency chest wall oscillation (HFCWO) devices in hospitals is consistently increasing. This study proposes a cost-effective actuator-less HFCWO device that utilizes an external wall port utility in hospitals to generate the positive and negative pneumatic pressures required for HFCWO treatment instead of an embedded mechanical actuator. The manufactured prototype with the no-amplification (NO-AMP) setting contained an electric pressure regulator to enable intensity level adjustment and two solenoid valves to enable vibration frequency adjustment, whereas the prototype with the pre-amplification (PRE-AMP) setting contained an additional air reservoir and an air-pressure booster. The prototype device was tuned to output average local maximum values in the pressure waveform similar to a commercial VEST-205 device at an 8-12 Hz frequency and 2-4 pressure intensity levels. In vitro comparative experiments demonstrated that the prototype device showed similar local maximum pressures to those of the VEST-205 (mean absolute pressure difference, <3 mmH2O); in contrast, the proposed device showed significantly higher local minimum pressures than those of the VEST-205 (mean absolute pressure difference, >8 mmH2O). Additionally, the driving sound of the proposed device was 17.0-17.8 dB higher than that of VEST-205. We conclude that the proposed device has the potential to substitute for conventional HFCWO devices under the limited but most frequently used operating conditions, although more detailed modifications are necessary in future studies to improve its performance and clinical usability.

Observation of negative differential Resistance(NDR) in chemically synthesized CuGaSe2 nanorods

CuGaSe2 nanorods has been synthesized through chemical bath deposition method using PVP(polyvinylpyrrolidone) as capping agent. Formation of CuGaSe2 nanorods was confirmed by SEM and TEM analysis. A systematic electrical study has been done on CuGaSe2 nanostructure by changing the Cu to Ga(%) composition ratio from CuSe2 to GaSe nanostructure. I-V characteristics showed that CuGaSe2 nanorods exhibit a negative differential resistance(NDR) region and their peak/valley ratio increases with Ga(%) composition. The occurrence of the NDR region is due to the electron tunneling through the potential barrier of Cu/CuGaSe2 interface. The increase in peak current in NDR region in CuGaSe2 nanorods with the increase in Ga(%) makes them suitable application in building oscillator and memory devices.

Modeling the effects of external oscillations on mucus clearance in obstructed airways.

Various therapeutic methods are employed to facilitate the clearance of secretions accumulated in the respiratory tracts of individuals with lower respiratory tract disorders. High-frequency chest wall oscillation (HFCWO) device, designed to apply variable amplitude and frequency vibrations to the individuals' chests, stands out among these therapies. In this study, the effectiveness of this treatment method was investigated numerically using computational fluid dynamics (CFD) on the generated mucus-obstructed bronchial geometry. The conducted analyses compared the effects of vibrations acting in the axial, radial, and tangential directions on the clearance of mucus, which exhibits non-Newtonian flow behavior with shear-thinning properties. Simultaneously, the effects of changes in vibration amplitude and frequency, pressure differentials, fluid properties, and ciliary movements on the flow were separately examined and interpreted. The findings demonstrate that ciliary movements are insufficient in mucus-accumulated airways, applied vibrations enhance mucus clearance, and potential improvements in flow are quite sensitive to boundary conditions.

Design a microwave transmitter using magnetron and two layers waveguides

A magnetron is a power oscillator device used in several radar transmitters for generating the electromagnetic wave (EMW) with a constructive and fixed frequency. In this work, a radar transmitter has been carried out using magnetron operates at 2,458 MHz and two conducting layers waveguides to achieve minimum loss of the signal due to the increased temperature. The magnetron is connected with the high voltage capacitor (1.0 μF) in order to store the alternating current (AC) signal delivered from the high voltage transformer. A waveguide parts have been used as transmission lines in view of connecting the magnetron to the antenna. These parts include two metal layers, the upper layer (outer) is advanced audio coding (AAC) 1350 aluminum conductor and the lower (inner) is copper. The waveguide dimension should be suitable to flow frequency from 2.2 GHz to 3.3 GHz. To measure the operating frequency, a waveguide adapter and a coaxial cable which combined with n-female connector have been connected to magnetron. The wave is delivering to the frequency counter by Bayonet Neill–Concelman (BNC) to n-female connectors. The promising results of the proposed work have been achieved with a maximum power, efficient return loss, acceptable voltage standing wave ratio (VSWR) and low-cost manufacturing.

Frequency Tunability of Spin‐Torque Vortex Oscillator in Permalloy Nanodisks with Modified Material Properties

The manipulation of the vortex state in magnetic nanostructures has received a lot of interest in recent decades, with potential applications in nonvolatile magnetic random‐access memory and logic networks. For wireless communication advancements, nano‐sized, and low‐phase‐noise, adjustable transmitter‐receiver networks are critical. Herein, it is shown that by using micromagnetic simulations when the saturation magnetization is reduced in a particular region of a magnetic nanodisk, the frequency tunability in such disks can be achieved. The gyrotropic mode of the vortex core is excited with spin‐polarized current and an in‐plane static magnetic field and found that an isolated magnetic vortex shows different resonance frequencies at different saturation magnetization regions. The dynamics of the mutual synchronization between two such dipolarly coupled magnetic vortices are numerically investigated, and the essential distances at which synchronization occurs are also identified. These incredibly small vortex‐based oscillator devices have linewidths of the order of 40–60 MHz, making them prospective candidates for signal‐processing applications and a strong new tool for basic research on vortex dynamics in magnetic nanostructures.

Enhancement of temperature-modulated NbO2-based relaxation oscillator via interfacial and bulk treatments

This work demonstrates oscillation frequency modulation in a NbO2-based relaxation oscillator device, in which the oscillation frequency increases with operating temperature and source voltage, and decreases with load resistance. An annealing-induced oxygen diffusion at 373 K was carried out to optimize the stoichiometry of the bulk NbO2 to achieve consistent oscillation frequency shift with device temperature. The device exhibits stable self-sustained oscillation in which the frequency can be modulated between 2 and 33 MHz, and a wider operating voltage range can be obtained. An additional surface treatment step was employed during fabrication to reduce the surface roughness of the bottom electrode and to remove surface contaminants that affect the interfacial properties of the device. The device frequency tunability coupled with high oscillating frequency and high endurance capability of more than 1.5 × 108 cycles indicates that the Pt/NbO2/Pt device is particularly suitable for applications in an oscillatory neural network.

Airway clearance therapy in the school environment: Retrospective analysis of a cohort of pediatric patients with cystic fibrosis

BackgroundAdherence to airway clearance therapy (ACT) in pediatric cystic fibrosis (CF) patients is reported to be below 50% and inability to sustain daily care is linked to poor health outcomes7,8,9. Through a collaboration between a CF care center and several schools, we hypothesized that ACT completed at school by pediatric CF patients will improve lung function while decreasing pulmonary exacerbations (PEx), days of antibiotics (abx) and hospitalizations. MethodsThis was a retrospective case-control study at a single CF care center consisting of 50 CF patients age < 18 at time when data was recorded (2012–2020). The case group used high-frequency chest wall oscillation or positive expiratory pressure devices at school for at least 1 year after self-reported or physician identified inadequate use at home. Lung function and measures of healthcare utilization were collected. ResultsIn the case group (n = 14), paired t-tests showed that after initiation of ACT at school, there were significant reductions in PEx requiring IV or PO abx (P = 0.010), total days of abx (P = 0.032), and visits to the CF care center (P = 0.037). There was no change in these outcomes in the matched control group (n = 36). ConclusionsThis is the first known study to highlight an initiative between a CF care center and schools which utilized airway clearance devices at school to ensure pediatric CF patients completed ACT. Through increased adherence, this relationship was associated with improved health outcomes. Use of alternative strategies may help patients with CF sustain adequate airway clearance.

Ten springs of experiments in CROCUS

Around a decade ago, a new team rebuilt experimental research at EPFL’s nuclear facilities, and in particular in the CROCUS nuclear reactor. After a broad investigation and open discussions with colleagues from the nuclear community, a number of experiments and research directions were selected. They range from reactor physics to nuclear data, with a focus on instrumentation. We present here the variety of experiments carried out and how instrumentation has been instrumental in these perspectives. Developments on branching or intrinsic reactor noise were made possible thanks to extensive theoretical investigation coupled with the developments of pulse and current modes neutron detection systems, as well as the LEAF gamma detection array. With regard to modulation or perturbation reactor noise, a study of fuel rods vibration was carried out thanks to the unique COLIBRI in-core fuel rods oscillation device; in the VOID experiments, a method was tested to measure the void coefficient with neutron modulation; in the APRHODITE project, the PISTIL rotating absorber, or absorber of variable strength, was used to determine the zero power reactor transfer function, in order to obtain feedback on kinetics nuclear data, particularly delayed neutrons. On the topic of nuclear data, the PETALE programme consisted on criticality and transmission experiments for the study of stainless steel, using instrumented metal reflectors. New dosimetry methodologies were developed for consistent and complete propagation of uncertainties, which also enabled experiments to be optimized. It will be continued in the HARVEST-X project, and its pile-oscillation program, BLOOM. Last but not least, developments in dosimetry as well as for a novel miniature neutron scintillation technology (MiMi detectors) allowed for interand intrapin (NECTAR) neutron measurements. 160 MiMi detectors have recently been distributed throughout the CROCUS core in a unique 3D detector array called SAFFRON, paving the way for novel high-resolution neutronics.

Hydroelastic response and electromagnetic energy harvesting of square oscillators: Effects of free and fixed square wakes

The unbounded linearly increasing responses in galloping instability make sharp-edge oscillators a beneficial solution for bladeless energy harvesting. While the performance of single square oscillators has been the subject of several studies in the past, there is still little knowledge about their hydrokinetic energy performance in tandem configurations. An optimal oscillator should display high performance in a group when all bodies are free to harness energy. In this study, the energy harvesting performance of square oscillators is examined in multiple tandem configurations under free and fixed square wakes. The harmonic oscillator model is coupled with the electromagnetic transducer to evaluate the performance of the system at the optimum coupling coefficient. For a single galloping square, flow interference by a similar upstream square affects the fluid elastic response of the oscillator and degrades its overall energy harvesting performance. The upstream fixed wake is productive in terms of efficiency (123% increase) but counterproductive for the electrical current and electromagnetic power. The free square wake generally diminishes both the power and efficiency. For a double tandem oscillator device, the synergy of tandem configuration at close spacing improves the maximum efficiency of the energy harvester by 97% as compared to two separate isolated oscillators.

Development of wind tunnel dynamic test system for coupled motion with multi-degrees of freedom

In view of the demand for complex aerodynamic data under high angle of attack in the development of advanced layout aircraft, the AVIC Aerodynamics Research Institute developed a three-degree-of-freedom large amplitude oscillation test system in the FL-51 low speed wind tunnel, which is mainly composed of a three-DOF oscillation device, a drive control system and a hydraulic power system, and can realize the single-DOF, two-DOF and three-DOF large amplitude oscillation test with a model at the scale of 1.5m under the wind speed range of 20m/s∼60m/s. According to the design input of the test system, the hardware scheme design of the drive system and control system, also the position servo control algorithm are designed, and the performance index debugging of the system is carried out. The three-DOF (Pitch, Yaw and Roll) large amplitude oscillation test was first realized in China with a low aspect ratio flying wing layout aircraft model. The debugging results show that the test system has excellent dynamic performance and multi-axis synchronization performance. The test results indicate that the test data obtained by the system is reasonable, and the performance indicators meet the requirements of the multi-degree-of-freedom coupled motion test in the process of aircraft development.

Design, simulation, and development of bipolar pulse forming network based Marx generator for S band backward wave oscillator.

Pulse power systems have a wide range of applications, one of which is microwave generation. Microwave emission is associated with a certain time delay between the application of a high voltage pulse and the generation of the microwave signal. This time delay is known as microwave delay time, and it depends on the time period of the microwave signal being generated. As the time period of the microwave signal increases, the required input electrical pulse duration also goes up. To achieve this, a pulse forming network (PFN) based Marx generator is proposed. The Bipolar Marx generator is preferred over the uni-polar Marx generator to obtain the high voltage high current pulse. This also helps in maintaining the impedance requirement for Backward Wave Oscillator (BWO) devices that generate the microwave pulse. To the best of our knowledge, PFN based Marx generators have been developed up to 400kV. Here, a bipolar Marx generator has been designed with ratings of 800kV peak voltage, 10kA peak current, and 150ns flattop pulse duration. The design includes analytical calculations and numerical analysis by electromagnetic simulation. The triggering method to get a wide triggering range has also been discussed. The design values have also been experimentally verified, and the resulting parameters were applied to a BWO to simulate the microwave power that it can produce. A peak microwave power of ∼1 GW has been observed in the particle-in-cell simulation.

Ultra-wide-band millimeter-wave generator using spin torque oscillator with strong interlayer exchange couplings

Recent increased development interest in millimeter-wave oscillator devices has necessitated realization of small oscillators with high frequency, wide frequency tunability, and room-temperature operation. Spin-torque oscillators (STOs) are fascinating candidates for such applications because of their nanometer size and suitability for room-temperature operation. However, their oscillation frequency and tunable range are limited to the order of 100 MHz–10 GHz. Here, we propose use of bilinear (J1) and biquadratic (J2) interlayer exchange couplings between ferromagnets in STOs to overcome these problems. The bilinear coupling contributes to oscillation frequency enhancement, whereas the biquadratic coupling facilitates frequency tunability via a current. Using micromagnetic simulation with parameters estimated from a material with small saturation magnetization, for J1 = 0 and J2 = − 1.0 mJ/m2, respectively, we find that the STO exhibits high frequency from 23 to 576 GHz and that its tunability reaches 61 GHz/(1011 A/m2) for current densities of − 0.5 to − 9.5 × 1011 A/m2. An analytical theory based on the macrospin model is also developed, which exhibits good quantitative agreement with the micromagnetic simulations. These results introduce new possibilities for spintronics applications in high-frequency devices such as next-generation mobile communications.

Shot noise of photonic heat transport through an oscillation device modulated by Majorana fermions

The photonic heat transport through an oscillation device under the modulation of Majorana bound states (MBSs) is investigated by using nonequilibrium Green’s function method. The photonic heat current correlation and shot noise formulas are derived. The overall behavior of heat shot noise is governed by terminal temperatures, while its detailed construction is modulated by the attached MBSs and oscillation device. The maximum values of heat current and shot noise are located at integer n times quantum flux Φ0, while they are modulated to zero at half integer of quantum flux (n+12)Φ0 due to changing magnetic flux. The Fano factor presents explicit nonlinear behavior by decreasing firstly to the minimum value and then increasing as the increase of temperature difference. The minimum value of Fano factor is raised up, while its position shifts towards zero temperature difference due to increasing terminal photon frequency. The monotonous enhancement of Fano factor valley is presented due to increasing the coupling constant λ between oscillation device and MBSs, while nonmonotonous variation of Fano factor valley is generated by adjusting the coupling energy ɛM of MBSs.

Lung Function Reference Equations for Indian Ethnic Groups Based on a Handheld Forced Oscillation Device for Age 9-19 Years.

To develop regression equations to predict forced oscillation technique (FOT) parameters in Indian children and adolescents. Lung function was assessed in a multigeographic cohort of residential school children using a portable FOT-based device (PulmoScan) and spirometry. FOT measurements were performed in 1497 study participants, aged 9-19 y, from 8 Indian districts. Bland-Altman analysis was performed for additional 32 adult subjects to compare the results of PulmoScan to a standard IOS device in an outpatient setting. Reference equations were developed for Rrs and Xrs from the data of healthy subjects with normal spirometry using multivariate regression model for Indo-European, Dravidian, and mixed ethnic groups. X5 (bias = 0.02) showed a better agreement than resistance parameters (R5 bias = 0.75, R20 bias = -0.22) in IOS/PulmoScan comparison. Anthropometric variables (age, height, and weight) were positively correlated with reactance (X5) and negatively with resistance parameters (R5, R10, R15, and R20), with most associations being stronger in boys. Final regression model considered ethnicity as a key determinant along with anthropometry. Multiethnic reference equations were developed for Indian children aged 9-19 y based on a novel handheld FOT device.

High-Frequency Chest Wall Oscillation in Patients with COVID-19: A Pilot Feasibility Study.

Coronavirus 2019 disease presents in a spectrum that can range from mild viral infection to pneu- monia. Common symptoms of coronavirus disease 2019 pneumonia include cough, sputum, and shortness of breath. High-frequency chest wall oscillation is a pulmonary rehabilitation method used for the recovery of pulmonary functions and removal of secretions in the lungs. The aim of the study was to evaluate the efficacy of high-frequency chest wall oscillation on patients with coronavirus disease 2019 pneumonia. In this study, 100 patients, between 18 and 70 years old, with a positive polymerase chain reaction result for coronavirus disease 2019, were included. Standard medical treatment was applied to all patients. In group rehabilitation, high-frequency chest wall oscillation treatment was applied twice a day for 20 minutes for 5 days. No additional intervention was made to the control group. Pulmonary function tests and oxygenation were evaluated on the first and fifth days. Patients' high-flow oxygen, non-invasive mechani- cal ventilation, and invasive mechanical ventilation needs were evaluated and recorded. Compared with the control group, the forced expiratory volume in 1 second, forced vital capacity, and peak expiratory flow rates were statistically higher in the rehabilitation group on the fifth day (P < .05). On evaluating the oxygenation of patients, the fifth day to first-day oxygen saturation difference was signifi- cantly higher in rehabilitation group than in control group (P < .05). Furthermore, the number of patients who needed non-invasive mechanical ventilation was lower in the rehabilitation group (P < .05). This study demonstrated that pulmonary rehabilitation applied with the high-frequency chest wall oscillation device in patients with coronavirus disease 2019 in the early period contributed to the improvement of oxygenation by providing significant improvement as observed in the pulmonary function tests of the patients.

Optimal Spin Polarization for Spin–Orbit-Torque Memory and Oscillator

Spin–orbit-torque arising from in-plane polarized spin current has attracted considerable attention for its potential in high-performance magnetic random access memories and spin torque oscillators (STOs). Recent studies have shown that an out-of-plane spin polarization can be even more efficient to drive the magnetization dynamics. In this work, we thoroughly examine the effect of the out-of-plane polarized spin current through macro-spin simulations. We propose separately the desirable conditions of spin polarization for spintronic memory and oscillator devices. It is found that for memory applications, a comparable strength of out-of-plane and in-plane spin polarization is necessary to simultaneously achieve a reduced switching current density and a faster switching speed. Besides, in STOs, the presence of a sizable out-of-plane polarization can provide an increase of oscillation amplitude and/or an improvement on frequency tunability. Our results address the importance of deliberate control on the spin polarization in designing efficient spintronic devices.

Probing electromagnetic wave energy with an in-series assembly of thermoelectric devices

We study the interaction of radio waves, microwaves, and infrared laser light of power P and period τ with a macroscopic thermoelectric (TEC) device-based detector and probe the energy Pτ as being the energy of these electromagnetic (EM) waves. Our detectors are in-series assemblies of TEC devices. We treat these detectors as equivalent to capacitors and/or inductors. The energy Pτ enables characterizing detector’s parameters, such as equivalent capacitance, inductance, resistance, responsivities, effective power, and efficiency. Through various scaling procedures, Pτ also aids in determining the power P of the EM waves. We compare the performance of our detectors with that of other TEC devices and with radio- and microwave-sensitive devices reported in the current literature, such as spin–orbit torque and spin–torque oscillator devices, heterojunction backward tunnel diodes, and Schottky diodes. We observe that the performance of our detectors is inferior. However, the order of magnitude of our detector’s parameters is in reasonable agreement with those of other TEC and non-TEC devices. We conclude that TEC devices can be used to detect radio waves and that Pτ effectively captures the energy of the EM waves. Considering Pτ as the EM wave’s energy offers a classical approach to the interaction of EM waves with matter in which photons are not involved. With the EM wave’s energy depending upon two variables (P and τ), a similar response could be produced by, e.g., radio waves and visible light, leading to interesting consequences that we briefly outline.

An enhancement method of waveform simulation in dual-color laser field imaging based on Internet of Things

AbstractIn view of the fact that the existing methods are easy to be affected by nonlinear factors in the incident process of the light source, resulting in the received shock wave inconsistent with the reality and large calculation error, a two-color laser field imaging waveform simulation and enhancement method based on the Internet of things is proposed. According to the automatic transformation characteristics of augmented reality technology, the waveform simulation control process of two-color laser field imaging is constructed. The Gaussian distribution characteristics are used to analyze the target, the optical grid and double oscillation device are used to control the results, the spectrum Fourier transform is used to adjust the phase of the waveform, and finally the simulated modulated laser waveform is output. Through the comparison of laser waveform spectrum and peak value, the results show that this method is closest to the actual laser waveform, saves calculation time, and has good practical application effect.