Oscillation Waveform Research Articles

Experimental investigation on the steam condensation dynamic characteristics at low steam mass flux

An experimental study has been performed to investigate the dynamic characteristics of steam direct contact condensation at low steam mass flux. Visible steam bubble parameters can be identified through the image processing algorithm. The maximum dimensionless diameter of steam bubble is calculated and the analysis model of identifying condensation regime is developed to predict transition boundaries of steam chugging and oscillatory bubble regimes. The pressure oscillation waveforms in pipe and in pool are distinguished. In chugging regime, the pressure pulse wave transforms to continuous wave in pool as water temperature increasing, however, in oscillatory bubble regime, continuous wave becomes pulse wave because of increased bubble pulsation volume. The oscillation frequencies are obtained from four different methods of bubble dynamic parameters, pressure pulse periods, pressure frequency spectrums in pipe and in pool to reveal the oscillation mechanism. The low-frequency component in chugging regime increases with water temperature increasing, while the intermediate-frequency component in chugging regime and the frequency in bubble regime decreases.

Magnetic Coupling-Based Battery Impedance Measurement Method

The battery impedance is an important indicator of battery health status. In this paper, a magnetic coupling-based impedance measurement method for electrochemical batteries is proposed. Without affecting the energy injection stage, the designed suppression resistance can minimize the influence of the primary circuit response, and the under-damped oscillation waveform containing the battery impedance information can be directly obtained on the primary inductance. The change of the mutual inductance value within a certain range will not affect the measurement results. Therefore, the measurement system has high stability and robustness. By utilizing the discrete Fourier transform (DFT)-based algorithm to calculate the damped oscillation parameters, the battery impedance is accurately derived from the calculated attenuation coefficient and damped oscillation frequency. The accuracy of this method under different coupling parameters is analyzed and verified by simulation and experiment on a Li-ion battery, which could be employed to estimate the state of charge (SOC).

Conformation and Experiment on Non-sinusoidal Oscillation Waveform Function for Continuous Casting Mold

Conformation and Experiment on Non-sinusoidal Oscillation Waveform Function for Continuous Casting Mold

Short-Time Impedance Spectroscopy Using a Mode-Switching Nonsinusoidal Oscillator: Applicability to Biological Tissues and Continuous Measurement.

Herein, we propose an impedance spectroscopy method using a mode-switching nonsinusoidal oscillator and apply this method for measuring the impedance of biological tissues and continuous impedance measurement. To obtain impedance spectra over a wide frequency range, we fabricated a novel nonsinusoidal oscillator incorporating binary counters and analog switches. This oscillator could periodically switch oscillation frequency through the mode switching of the feedback resistor. From the oscillation waveform at each oscillation frequency of this circuit (oscillator), we determined the impedance spectrum of a measured object using the discrete-time Fourier transform. Subsequently, we obtained the broad impedance spectrum of the measured object by merging odd-order harmonic spectral components up to the 19th order for each oscillation frequency. From the measured spectrum, the resistive and capacitive components of the circuit simulating bioimpedance were estimated with high accuracy. Moreover, the proposed method was used to measure the impedance of porcine myocardium; changes in the impedance spectrum of the myocardial tissue due to coagulation could be measured. Furthermore, rapid variations in the resistance value of a CdS photocell could be continuously measured using the proposed method.

Experimental Study on the Effect of Lightning Impulse Oscillation Frequency on Pressboard Flashover in Oil

In this work, effect of the oscillation frequency on the oil surface flashover characteristics under lightning impulse voltage is experimentally studied. Four lightning impulse (OLI) waves with different oscillation frequencies and 1.2/50 μs standard lightning impulse (SLI) wave are used in this study. The experiment results show that flashover voltages under OLI are larger than those under SLI and the flashover time lags under OLI are longer than those under SLI. Additionally, the flashover voltage tends to increase and the time lag tends to be shorter as the oscillation frequency increases. According to the experimental results and the discharge theory of liquids, we believe that the waveform oscillation frequency affects both the effective electron generation time lag and the formative time lag. This work provides a reference for the waveform selection of the on-site withstand voltage test and explains the physical mechanism of the oil flashover discharge from the perspective of impulse waveform oscillation.

A Generalized Mode-Locking Theory for a Nyquist Laser With an Arbitrary Roll-Off Factor PART II: Oscillation Waveforms and Spectral Characteristics

In this paper (PART II), we present output waveforms and the corresponding spectrum of a periodic Nyquist pulse train with a roll-off factor α emitted from a mode-locked Nyquist laser. In the first part, the relationship between the optical filter amplitudes H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> installed in a Nyquist laser cavity is derived by using the inverse Fourier transformation of filter F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ( ω) at a low frequency edge and F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ( ω) at a high frequency edge. We found that the relationship H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> = (4/3) H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> for α = 0 is changed into the relationship H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> = (1/cos( β Ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> /2)) H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> for α ≠ 0, where β = π/( 2αω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> ), ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> is the zero-crossing frequency and Ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> is the modulation frequency. This relationship is important for describing the entire spectral profile of the optical filter installed in the laser cavity. In the latter part, we report how we succeeded in generating a Nyquist pulse train with an arbitrary α value by employing computer simulations with analytically derived optical filters consisting of F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ( ω) and F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ( ω), H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> , and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> . We found that a Nyquist laser cannot always generate an isolated ideal Nyquist pulse train because there is interference between the wings of adjacent Nyquist pulses. We clarify the differences and similarities as regards filter shape and the corresponding waveform in the time domain of a single Nyquist pulse and a periodic Nyquist pulse train in terms of differences in power P, time-domain distribution τ, spectrum S, and filter shape F. We show that a pure Nyquist pulse train can be obtained with the condition α N > 10, where differences in P, S, and F are less than 1 %, and we present a useful chart showing how to generate a Nyquist pulse train in the GHz region. N is the number of modes in the low or high frequency region. We investigated the time domain orthogonality g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m,n</sub> of the Nyquist pulse train from the laser and found that the orthogonality can be maintained although there is a small interference effect on the wing of the Nyquist pulse.

STFT Analysis of Broadband Oscillation in VSC-HVDC Connected to Offshore Wind Farms

The transmission technology of offshore windfarms (OWFs) through VSC-HVDC system is developing rapidly. The impact factor of broadband oscillation is complex, it often occurs in VSC-HVDC and direct drive permanent magnet synchronous generator (DDPMSG). In this paper, based on short time fourier transform (STFT), factors that cause broadband oscillation are studied. Firstly, the primary structure of DDPMSG and VSC-HVDC is established. Then the correctness of small signal method (SSM) is verified. Based on eigenvalue analysis, instability caused by controlling parameter is analysed. Finally, time-frequency characteristic of oscillation waveforms in PSCAD is extracted using STFT, asynchronous characteristics of broadband oscillation is verified. It is of guiding significance, for the developing technology of offshore wind farm integrated into grid through VSC-HVDC system.

Estimation of pulsatile energy dissipation in intersecting pipe junctions using inflow pulsatility indices

This study aims to characterize the effect of inflow pulsatility on the hydrodynamic power loss inside intersecting double-inlet, double-outlet pipe intersection (DIPI) with cross-flow mixing. An extensive set of computational fluid dynamics (CFD) simulations was performed in order to identify the individual effects of flow pulsatility parameters, i.e., amplitude, frequency, and relative phase shift between the inflow waveform oscillations, on power loss. An experimentally validated second order accurate solver is employed in this study. To predict the pulsatile flow performance of any given arbitrary inflow waveforms, we proposed three easy-to-calculate pulsatility indices. The frequency-coupled quasi-steady flow theory is incorporated to identify the functional form of pulsatile power loss as a function of these indices. Our results indicated that the power loss within the inflow branch sections, lumped outflow-junction section, and the whole conduit correlates strongly with the pulsatility of each inflow waveform, the total inflow pulsatility, and inflow frequency content, respectively. The complete CFD simulation matrix provided a unified analytical expression that predicts pulsatile power loss inside a one-degree offset DIPI geometry. The predictive accuracy of this expression is evaluated in comparison to the CFD evaluation of arbitrary multi-harmonic inflow waveforms. These results have important implications on hydrodynamic pipe networks that employ complex junctions as well as in the patient-to-patient comparison of surgically created vascular connections. Coupling the present analytical pulsatile power loss expression with non-dimensional steady power loss formulation provided a valuable predictive tool to estimate the pulsatile energy dissipation for any arbitrary junction geometry with minimum use of the costly CFD computations.

Oscillator Flicker Phase Noise: A Tutorial

A deep understanding of how to reduce flicker phase noise (PN) in oscillators is critical in supporting ultra-low PN frequency generation for the advanced communications and other emerging high-speed applications. Unfortunately, the current literature is either full of conflicting theories and ambiguities or too complex in mathematics, hiding the physical insights. In this brief, we comprehensively review the evolution of flicker noise upconversion theories and clarify their controversial and confusing parts. Two classes of such upconversion mechanisms in voltage-biased LC-tank oscillators (nMOS-only and complementary) are specifically compared and numerically verified using a commercial simulation model of 28-nm CMOS. We identify that non-resistive terminations of both 2nd and 3rd harmonic currents contribute to oscillation waveform asymmetries that lead to the flicker noise upconversion. Further, we discuss three 1/f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> PN reduction mechanisms: waveform shaping, narrowing of conduction angle, and gate-drain phase shift.

Capacitive-Coupling Impedance Spectroscopy Using a Non-Sinusoidal Oscillator and Discrete-Time Fourier Transform: An Introductory Study.

In this study, we propose a new short-time impedance spectroscopy method with the following three features: (1) A frequency spectrum of complex impedance for the measured object can be obtained even when the measuring electrodes are capacitively coupled with the object and the precise capacitance of the coupling is unknown; (2) the spectrum can be obtained from only one cycle of the non-sinusoidal oscillation waveform without sweeping the oscillation frequency; and (3) a front-end measuring circuit can be built, simply and cheaply, without the need for a digital-to-analog (D-A) converter to synthesize elaborate waveforms comprising multiple frequencies. We built the measurement circuit using the proposed method and then measured the complex impedance spectra of 18 resistive elements connected in series with one of three respective capacitive couplings. With this method, each element’s resistance and each coupling’s capacitance were estimated independently and compared with their nominal values. When the coupling capacitance was set to 10 nF or 1.0 nF, estimated errors for the resistive elements in the range of 2.0–10.0 kΩ were less than 5%.

Electrochemical machining of a rhombus hole with synchronization of pulse current and low-frequency oscillations

Abstract Metal gratings with rhombus holes are widely applied in lightweight aircraft components. Electrochemical machining (ECM) is a nontraditional processing technology with no tool loss and no thermal deformation that has unique advantages for the high-quality processing of rhombus holes. However, the flow paths of the electrolyte in the lateral gap are quite different, and stray corrosion easily occurs on the sidewall due to the different diagonal lengths of a rhombus hole. In this paper, a method was proposed to improve the flow field and processing localization by the synchronization of the pulse power supply and low-frequency oscillations. The on and off positions of the pulse power supply are symmetrical with respect to the wave trough of the oscillation waveform. Based on the coupled simulation of the gas-liquid two-phase flow field and electric field, the effects of assisting oscillations and synchronization of the pulses and oscillations on the void fraction, electrical conductivity, current density, dissolution rate and evolution of the anode profile were investigated. Moreover, the effects of assisting oscillations and synchronization of the pulses and oscillations on the lateral gap, sidewall slope, machining fillet and surface quality were experimentally studied. The experimental results of different ECM methods showed that the coupled simulation was effective and feasible. Moreover, the simulation analysis and experimental results both revealed that the processing accuracy and surface quality of a rhombus hole could be improved by using the synchronized ECM method. The lateral gap at the rhombus hole entrance was only 0.13 mm, the sidewall slope was 0.026 and the surface roughness was Ra0.134 μm under the optimized parameters.

Construction of Nonsinusoidal Oscillation Waveform Function and Technological Parameters for Continuous Casting Mold

Nonsinusoidal oscillation techniques can shorten the negative strip time and improve the slab surface quality in the process of steel continuous casting. But the acceleration of nonsinusoidal oscillation is higher than that of the sinusoidal oscillation. So it is easy to result in the impact for the mold movement. To solve this problem, a nonsinusoidal oscillation waveform function of mold was constructed, which had good dynamic characteristics. And the smaller acceleration can reduce the impact of the oscillator. By analyzing the parameters of oscillation technology, the calculation method of each oscillation technological parameter for seven section functions was presented and the multitechnological parameter curves were given. Based on the technological parameters of sinusoidal oscillation, a synchronous control model of nonsinusoidal oscillation was determined. The results show that the parameters can satisfy the limit value in theory, which can enhance the casting speed, surface quality of slab, and provide reference for further practice in industry.

Oscillatory spontaneous dimpling in evaporating curved thin films

We examine the dynamics of a thin film composed of a non-evaporative silicone oil (high surface tension) with trace amounts of an evaporative silicone oil (low surface tension) over an air bubble. An evaporating thin liquid film is formed atop a capillary-pinned air bubble by squeezing then holding the bubble against the air–silicone oil interface. Despite the simplicity of the system, complex oscillatory dynamical behaviour has been observed. Through interferometric experiments and numerical simulations, we show that as the bubble is moved towards the opposite interface, a dimple forms and during the subsequent holding period the dimple spontaneously oscillates. The evaporation-driven solutal–thermal Marangoni flow thickens the film and capillarity subsequently discharges the dimple. Solutal and thermal Marangoni flows both contribute to film thickening and as the local concentration of the non-evaporative species increases, the strength of the Marangoni flows increases. The oscillation frequency and waveform depend on initial composition and the maximum dimple volume. We suggest that these oscillatory solutions and the associated mechanism are a partial explanation for the film stabilization in multicomponent oils, reported experimentally in a recent publication (Chandran Suja et al., Proc. Natl Acad. Sci., vol. 115, 2018, pp. 7919–7924).

Comparison of Hafnium Dioxide and Zirconium Dioxide Grown by Plasma-Enhanced Atomic Layer Deposition for the Application of Electronic Materials

We report the growth of nanoscale hafnium dioxide (HfO2) and zirconium dioxide (ZrO2) thin films using remote plasma-enhanced atomic layer deposition (PE-ALD), and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using the HfO2 and ZrO2 thin films as the gate oxide. Tetrakis (dimethylamino) hafnium (Hf[N(CH3)2]4) and tetrakis (dimethylamino) zirconium (IV) (Zr[N(CH3)2]4) were used as the precursors, while O2 gas was used as the reactive gas. The PE-ALD-grown HfO2 and ZrO2 thin films were analyzed using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The XPS measurements show that the ZrO2 film has the atomic concentrations of 34% Zr, 2% C, and 64% O while the HfO2 film has the atomic concentrations of 29% Hf, 11% C, and 60% O. The HRTEM and XRD measurements show both HfO2 and ZrO2 films have polycrystalline structures. n-channel and p-channel metal-oxide semiconductor field-effect transistors (nFETs and pFETs), CMOS inverters, and CMOS ring oscillators were fabricated to test the quality of the HfO2 and ZrO2 thin films as the gate oxide. Current-voltage (IV) curves, transfer characteristics, and oscillation waveforms were measured from the fabricated transistors, inverters, and oscillators, respectively. The experimental results measured from the HfO2 and ZrO2 thin films were compared.

Adaptive Repetitive Control of A Linear Oscillating Motor under Periodic Hydraulic Step Load.

A linear oscillating motor has a direct and efficient linear motion output and is widely used in linear actuation systems. The motor is often applied to compact hybrid electrohydraulic actuators to drive a linear pump. However, the periodic switch of the rectification valve in the pump brings the hydraulic step load to the linear motor, which causes periodic oscillation waveform distortions. The distortion results in the reduction of pumping capacity. The conventional feedback proportional-integral-derivative control is applied to the pump, however, this solution cannot handle the step load as well as resolving nonlinear properties and uncertainties. In this paper, we introduce a nonlinear model to identify periodic hydraulic load. Then, the loads are broken up into a set of simple terms by Fourier series approximation. The uncertain terms and other modeling uncertainties are estimated and compensated by the practical adaptive controller. A robust control term is also developed to handle uncertain nonlinearities. The controller overcame drawbacks of conventional repetitive controllers, such as heavy memory requirements and noise sensitivity. The controller can achieve a prescribed final tracking accuracy under periodic hydraulic load via Lyapunov analysis. Finally, experimental results on the linear oscillating motor-pump are provided for validation of the effectiveness of the scheme.

Physical-Based Simulation of the GaN-Based Grooved-Anode Planar Gunn Diode.

In this paper, a novel gallium nitride (GaN)-based heterostructure Gunn diode is proposed for the first time to enhance the output characteristics of Gunn oscillation waveforms. A well-designed grooved anode contact is adopted to separate the long-channel diode into two short-channel diodes in parallel. If the grooved anode contact is positioned in the middle of the device, the output power nearly doubles in the grooved-anode diode compared with the single-channel ones, as does the output frequency. Based on the numerical results, the best output characteristics are obtained at the 2.0-µm symmetrical grooved-anode diode, which produces nearly 5.48 mW of power at the fundamental frequency of 172.81 GHz, with 3.13% efficiency of power conversion. If the grooved anode contact is not positioned in the middle of the diode, the harmonic frequency would be enhanced. The GaN heterostructure grooved-anode Gunn diode has been demonstrated to be an excellent solid-state source of terahertz oscillator.

Investigation of Non-Sinusoidal Oscillator Driven by Double Servomotors for Continuous Casting Mold

To improve the surface quality and casting speed of the slab further, a new type mold oscillator synchronously driven by double servomotors was proposed in this paper. The experimental prototype was designed and manufactured. For the non-sinusoidal oscillator, the waveform modification ratio could be adjusted during the steel continuous casing operation. Firstly, the working principle of the oscillator was described. Secondly, the rotating rules of the servomotor to realize non-sinusoidal oscillation waveform for entire function were given. Finally, the laboratory experiments were made. The experiment results show that the error of the two-side oscillation curves is smaller and the actual technological parameters are close to the theory and the oscillator can realize non-sinusoidal oscillation well. This kind of non-sinusoidal oscillator provides a feasible scheme for reducing oscillator investment, increasing casting speed and enhancing slab quality.

Research on hybrid SHEPWM based on different switching patterns

&lt;span&gt;This paper presents a hybrid pulse width modulation (HPWM) strategy based on different switching patterns of selective harmonic elimination pulse width modulation (SHEPWM) for the three-level neutral point clamped (3L-NPC) converter. Specific low-order harmonics can be eliminated by SHEPWM at low switching frequency, while the remaining high-order harmonics can be selected to be simply filtered by additional hardware. Large oscillation waveform usually occurs in the transition instant between two diverse modulation situations, therefore switching between distinct switching patterns can be problematic if no effective means is taken, especially when the effect of smooth and fast transition at any time is considerable. A universal and valid control strategy, which maintains the high-quality output voltage and current, is proposed and implemented in this paper to address this issue. Simulation results obtained from MATLAB/SIMULINK are presented to analyze the performance and validate the feasibility and effectiveness of this control scheme.&lt;/span&gt;

Intuitive Understanding of Flicker Noise Reduction via Narrowing of Conduction Angle in Voltage-Biased Oscillators

This brief aims to intuitively explain and numerically verify the observed phenomenon of flicker noise reduction in oscillators of reduced conduction angle (i.e., in class-C), which has been presented in literature but never properly explained. The flicker phase noise in a voltage-biased oscillator capable of operating in class-B and class-C is compared and numerically verified using a commercial simulation model of TSMC 28-nm CMOS. We illustrate how narrowing the conduction angle can suppress the $1/{f}$ noise up-conversion by decreasing $1/{f}$ noise exposure to the asymmetric rising and falling edges of oscillation waveform. The effects of implicit common-mode tank in the class-C operation is also discussed. We further clarify ambiguities among several simulation methods of impulse sensitivity function (ISF) based on periodic small-signal analysis [periodic AC or periodic transfer function (PXF)], which is a key tool in understanding the flicker noise up-conversion. A clearer ISF simulation method based on positive sidebands of PXF is proposed.

Mass and Energy Densities of the Cosmos

Fundamental principles of classical (Newtonian) physics are employed to probe the cosmological lambda &amp;Lambda;; it yields the values &amp;rho;vac = 2.61 x 10-39 g cm-3 and &amp;Lambda; = 4.87 x 10-66 cm-2. It is revealed that &amp;Lambda; is a fundamental physical constant defined by vacuum density-light speed &amp;rho;vacc2 correlation. However, the constant accelerates along the groups and periods of a universal spatial periodicity equivalent to the chemical periodicity. Previous results are cited to show that chemical elements are quantum harmonic (periodic) oscillators QHOs and their waveform oscillations exclusively define the vacuum field. The cosmological periodic unit CPU is introduced, it relies on the cosmological principle to argue that a relative physical quantity evaluated for the QHO applies to constituents of corresponding cosmological spatial quanta. Compelling evidences, backed with relevant data and quantitative expressions, are presented to argue that: there was never a big bang, it is a Linde-universe sans &amp;ldquo;chaotic&amp;rdquo;; nature posts no singularity; mass does not curve spacetime, neither does metric space curvature trace directly to gravitation nor particle creation, gravity is classical, not quantum; reality is quadri-phasic not mono-phasic with a clear distinction between the atomic waveform defined with absolute atomic mass and condensed matter defined with relative atomic mass; every chemical element exists in three particle-generations thus, dark matter is invisible form (conjugate) of the visible element, its waveform manifests dark energy, it is not implicated in metric space expansion; Planck scale does not exist, radioactivity constrains fundamental length to atomic radius of the heaviest element.