Showing papers on "Sine wave published in 2009"

The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms

Abstract: The Lomb-Scargle periodogram is a common tool in the frequency analysis of unequally spaced data equivalent to least-squares fitting of sine waves. We give an analytic solution for the generalisation to a full sine wave fit, including an offset and weights (χ 2 fitting). Compared to the Lomb-Scargle periodogram, the generalisation is superior as it provides more accurate frequencies, is less susceptible to aliasing, and gives a much better determination of the spectral intensity. Only a few modifications are required for the computation and the computational effort is similar. Our approach brings together several related methods that can be found in the literature, viz. the date-compensated discrete Fourier transform, the floating-mean periodogram, and the “spectral significance” estimator used in the SigSpec program, for which we point out some equivalences. Furthermore, we present an algorithm that implements this generalisation for the evaluation of the Keplerian periodogram that searches for the period of the best-fitting Keplerian orbit to radial velocity data. The systematic and non-random algorithm is capable of detecting eccentric orbits, which is demonstrated by two examples and can be a useful tool in searches for the orbital periods of exoplanets.

Ideal waveform to generate the maximum possible electron recollision energy for any given oscillation period

Abstract: We present the perfect waveform which, during a strong field interaction, generates the maximum possible electron recollision energy for any given oscillation period, over 3 times as high as that for a pure sinusoidal wave. This ideal waveform has the form of a linear ramp with a dc offset. A genetic algorithm was employed to find an optimized practically achievable waveform composed of a longer wavelength field, to provide the offset, in addition to higher frequency components. This second waveform is found to be capable of generating electron recollision energies as high as those for the perfect waveform while retaining the high recollision amplitudes of a pure sinusoidal wave. Calculations of high harmonic generation demonstrate this enhancement, by increasing the cutoff energy by a factor of 2.5 while maintaining the harmonic yield, providing an enhanced tool for attosecond science.

Precision Differential Sampling Measurements of Low-Frequency Synthesized Sine Waves With an AC Programmable Josephson Voltage Standard

Abstract: We have developed a precision technique to measure sine-wave sources with the use of a quantum-accurate AC programmable Josephson voltage standard. This paper describes a differential method that uses an integrating sampling voltmeter to precisely determine the amplitude and phase of high-purity and low-frequency (a few hundred hertz or less) sine-wave voltages. We have performed a variety of measurements to evaluate this differential technique. After averaging, the uncertainty obtained in the determination of the amplitude of a 1.2 V sine wave at 50 Hz is 0.3 muV/V (type A). Finally, we propose a dual-waveform approach for measuring two precision sine waves with the use of a single Josephson system. Currently, the National Institute of Standards and Technology (NIST) is developing a new calibration system for electrical power measurements based on this technique.

Dual synchro-resonant electrosurgical apparatus with bi-directional magnetic coupling

Abstract: An electrosurgical generator is disclosed. The electrosurgical generator includes a power supply for generating a DC voltage. The electrosurgical generator also includes a first parallel inductor-capacitor circuit being driven by a first signal at a first predetermined frequency and a second parallel inductor-capacitor circuit driven by a second signal at the first predetermined frequency phase shifted 180 degrees. The electrosurgical generator further includes a series inductor-capacitor resonant circuit operably connected in series with a primary winding of a transformer. The first and second parallel inductor-capacitor circuits are operably connected to the transformer, such that the first inductor-capacitor circuit generates a positive half sine wave and the second inductor-capacitor circuit generates a 180 degrees phase-shifted positive half sine wave to generate a full sine wave in a secondary winding of the transformer.

The transfer of current through skin and muscle during electrical stimulation with sine, square, Russian and interferential waveforms

Abstract: Electrical stimulation is a commonly used modality for both athletic training and physical therapy. However, there are limited objective data available to determine the waveform which provides the maximum muscle strength as well as minimizing pain. In the present investigation, two groups of subjects were examined. Group 1 was composed of six males and four females and group 2 was composed of three male and three female subjects. The first series of experiments investigated muscle strength with stimulation at currents of 20, 40 and 60 milliamps using sine, square, Russian and interferential waveforms evaluating strength production and pain as outcomes. The second phase of experiments compared the effect of the different waveforms on current dispersion in surface versus deep muscle electrodes with these same waveforms. The results of the experiments showed that sine wave stimulation produced significantly greater muscle strength and significantly less pain than square wave, Russian or interferential stimulation at that same current. The most painful stimulation was square wave. Strength production was greatest with sine wave and least with Russian and interferential. An explanation of these findings may be the filtering effect of the fat layer separating skin from muscle. The highly conductive muscle and skin dermal layers would form the plates of a capacitor separated by the subcutaneous fat layer providing an RC filter. This filtering effect, while allowing sine wave stimulation to pass to the muscle, reduced power transfer in square wave, Russian and interferential stimulation is observed.

Airfoil Flow Experiment on the Duty Cycle of DBD Plasma Actuator

Abstract: The parameters of DBD (Dielectric Barrier Discharge) plasma actuator with burst wave (duty cycle) are investigated by the low speed wind tunnel experiment for airfoil. In this paper, influence of burst frequency f, input voltage sine wave frequency fbase and burst ratio BR on the stall control are discussed. The experiments are conducted with the conditions Rec=44,000, 63,000. The actuator is applied to NACA0015 airfoil and then flow-fields around the airfoil are visualized by the smoke wire method and pressure around its surface is measured by the multipoint steady pressure measurement. The results show that within the present experimental conditions, the higher f and fbase are more effective in the separation control and the smaller BR has the stronger separation control capability in spite of less input energy. In present conditions, the optimum dimensionless burst wave frequency F is 9.1. This result shows the same tendency as the result of Sidorenko, et al.

Vector sum phase shifter, optical transceiver, and control circuit

Abstract: A vector sum phase shifter includes a 90° phase shifter ( 1 ) which generates an in-phase signal (VINI) and a quadrature signal (VINQ) from an input signal (VIN), a four-quadrant multiplier ( 2 I) which changes the amplitude of the in-phase signal (VINI) based on a control signal (CI), a four-quadrant multiplier ( 2 Q) which changes the amplitude of the quadrature signal (VINQ) based on a control signal (CQ), a combiner ( 3 ) which combines the in-phase signal (VINI) and the quadrature signal (VINQ), and a control circuit ( 4 ). The control circuit ( 4 ) includes a voltage generator which generates a reference voltage, and a differential amplifier which outputs the difference signal between a control voltage (VC) and the reference voltage as the control signal (CI, CQ). The differential amplifier performs an analog operation of converting the control voltage (VC) into the control signal (CI, CQ) similar to a sine wave or a cosine wave.

Square wave-sine wave signal converting method and converting circuit

Abstract: The invention discloses a square wave-sine wave signal transformation method comprising the steps as follows: a square wave signal generates N square wave control signals with the same period; the N square wave control signals arrayed in sequence respectively generate N square wave secondary signals; the amplitude sum of the N square wave secondary signals is a; the amplitude of the square wave signal n is a right type; the N square wave secondary signals are processed through superposition to obtain a false sine wave signal; and the false sine wave signal is processed through filtration to obtain a sine wave signal. A square wave-sine wave signal transformation circuit is also disclosed, and the superposition of the N square wave secondary signals in the method is realized by controlling the superposition of current so as to obtain the sine wave signal. The square wave-sine wave signal transformation method and the square wave-sine wave signal transformation circuit avoid adopting a higher order high-frequency filter directly, greatly save the area and the power consumption of a chip, and reduce the design complexity.

Fourier Transform Infrared (FTIR) Spectroscopy

Abstract: Fourier transform infrared (FTIR) spectroscopy is considered to be one of the most powerful techniques for chemical analysis in recent years, and is making new inroads into several applications in biological analysis, including food. Fourier transformation (FT) is a mathematical procedure that is applied to the interferograms to obtain the spectrum. Essentially, FT breaks down the interferogram provided by the interferometer into sine waves for each wavelength in the light. These sine waves are arranged over the wavelength to produce the conventional spectrum. Many different types of materials and components are available for FTIR construction. The important components of an FTIR spectrometer are the interferometer, source, beam splitter, detector, and laser. One of the most important components of interferometer is the moving mirror that is required to control its position precisely in order to obtain an accurate measurement of spectra. The function of the detector is to transduce the light intensity received by it to electrical signal. Two most commonly used detectors in both FT-near-infrared (FT-NIR) and FT-mid-infrared (FT-MIR) instruments are the deuterated triglycine sulfate (DTGS), detectors and the mercury cadmium telluride (MCT) detectors.

Josephson-Voltage-Standard-Locked Sine Wave Synthesizer: Margin Evaluation and Stability

Abstract: This paper describes a Josephson-voltage-standard-locked synthesizer where a commercial digital-to-analog converter is used as a sine wave generator. The output amplitude of the generator is controlled by the calculable fundamental of the stepwise waveform generated by a SINIS Josephson junction array. Such a system combines the versatility of a commercial source with the stability and accuracy of the Josephson standard. By discarding the measurements performed during the transients, broad voltage steps of 1.7 mA were obtained up to frequencies of 500 Hz.

Design and implementation of microcontroller based PWM technique for sine wave inverter

Abstract: A microcontroller based advanced technique of generating sine wave with minimized harmonics is implemented in this paper. The proposed technique “impulse-sine product” aims to design and implement a voltage regulated inverter with ripple free and glitch free output sine wave that can operate electronic devices efficiently. The output voltage of the inverter is regulated by a feedback loop using analog to digital protocol of PIC16f877 microcontroller. The design is essentially focused upon low power electronic appliances such as personal computers, chargers, television sets. The inverter output is regulated from 16-volt rms to 220-volt rms for a variation of load between 1-Ω to 180-Ω loads. The designed inverter provides a range of operation from 25 Watts to 250 Watts. The design is mathematically modeled which is simulated in Matlab, Proteus and finally the results are practically verified.

Three-dimensional blast-wave-driven Rayleigh-Taylor instability and the effects of long-wavelength modes

Abstract: This paper describes experiments exploring the three-dimensional (3D) Rayleigh–Taylor instability at a blast-wave-driven interface. This experiment is well scaled to the He/H interface during the explosion phase of SN1987A. In the experiments, ∼5 kJ of energy from the Omega laser was used to create a planar blast wave in a plastic disk, which is accelerated into a lower-density foam. These circumstances induce the Richtmyer–Meshkov instability and, after the shock passes the interface, the system quickly becomes dominated by the Rayleigh–Taylor instability. The plastic disk has an intentional pattern machined at the plastic/foam interface. This perturbation is 3D with a basic structure of two orthogonal sine waves with a wavelength of 71 μm and an amplitude of 2.5 μm. Additional long-wavelength modes with a wavelength of either 212 or 424 μm are added onto the single-mode pattern. The addition of the long-wavelength modes was motivated by the results of previous experiments where material penetrated unexpectedly to the shock front, perhaps due to an unintended structure. The current experiments and simulations were performed to explore the effects of this unintended structure; however, we were unable to reproduce the previous results.

The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms

Abstract: The Lomb-Scargle periodogram is a common tool in the frequency analysis of unequally spaced data equivalent to least-squares fitting of sine waves. We give an analytic solution for the generalisation to a full sine wave fit, including an offset and weights ($\chi^{2}$ fitting). Compared to the Lomb-Scargle periodogram, the generalisation is superior as it provides more accurate frequencies, is less susceptible to aliasing, and gives a much better determination of the spectral intensity. Only a few modifications are required for the computation and the computational effort is similar. Our approach brings together several related methods that can be found in the literature, viz. the date-compensated discrete Fourier transform, the floating-mean periodogram, and the "spectral significance" estimator used in the SigSpec program, for which we point out some equivalences. Furthermore, we present an algorithm that implements this generalisation for the evaluation of the Keplerian periodogram that searches for the period of the best-fitting Keplerian orbit to radial velocity data. The systematic and non-random algorithm is capable of detecting eccentric orbits, which is demonstrated by two examples and can be a useful tool in searches for the orbital periods of exoplanets.

Modeling and Measuring Error Contributions in Stepwise Synthesized Josephson Sine Waves

Abstract: Synthesizing Josephson stepwise approximated sine waves to produce an AC quantum standard is limited by errors in the waveform transitions between quantized voltages. Many parameters have an impact on the shape of the transients. A simple model with a single equivalent time constant can be used to evaluate the influence of these parameters. Measurements of the transients allow establishment of the value of the equivalent time constant and prediction of the response to variations of the parameters. We have experimentally confirmed the influence of changes in the bias current used for the quantized voltages and in the microwave power applied. Under usual operating conditions, the model predicts that increasing the number of samples per period nonlinearly reduces the difference between measured and ideal root-mean-square (rms) values. This behavior was confirmed through measurements with thermal converters.

A Bit-Stream-Based PWM Technique for Sine-Wave Generation

Abstract: A new method for the generation of high-quality sinusoidal signals is presented. Multibit binary signals are represented using uniformly weighted single bit streams that can then be processed by digital logic. Building blocks that are useful for the construction of the sinusoidal generator are also presented. The bit-stream representation has the advantage of having the characteristics of a classical pulsewidth-modulation signal and hence can be used to drive high-power switching devices with minimal conditioning. The technique is simple and can easily be implemented using digital logic on a field-programmable gate array (FPGA). The operation of a single-phase inverter using the proposed technique is demonstrated using an Altera Stratix FPGA and a custom-built power stage. The complete digital design uses less than 200 logic elements. The performance of this technique is quantified using simulations and practical measurements. Practical implementations lead to total harmonic distortion measures ranging between 0.75% and 4.92%.

A Phase-Amplitude Iteration Scheme for the Optimization of Deterministic Wave Sequences

Abstract: For the deterministic investigation of extreme events like capsizing, broaching or wave impacts, methods for the generation of deterministic wave sequences are required. These wave sequences can be derived from full scale measurements, numerical simulations or other sources. Most methods for the generation of deterministic wave sequences rely as a backbone on linear wave theory for the backwards transformation of the wave train from the target position in the wave basin to the position of the wave maker. This implies that nonlinear wave effects are not covered to full extend or they are completely neglected. This paper presents a method to improve the quality of the generated wave train via an experimental optimization. Based on a first wave sequence generated with linear wave theory and measured in the wave basin, the phases and amplitudes of the wave maker control signal are modified in frequency domain. The iteration scheme corrects both, shifts in time and in location, resulting in an improved deterministic wave train at the target location. The paper includes results of this method from three different basins with different types of wave generators, water depth and model scales. In addition, this method is applied to a numerical wave tank where the waves can be optimized before the actual basin testing.Copyright © 2009 by ASME

Method of pre-reconstruction decomposition for fast kV-switching acquisition in dual energy computed tomography (CT)

Abstract: Fast kV-switching is a dual energy acquisition technique in computed tomography (CT) in which alternating views correspond to the low and high tube voltages. Its high temporal resolution and its suitability to a variety of source trajectories make it an attractive option for dual energy data acquisition. Its disadvantages include a one-view misregistration between the data for high and low voltages, the potentially poor spectrum separation due to the more-like a sine wave rather than the desired square wave in fast kV-switching, and the higher noise in the low voltage data because of the technical difficulty in swinging the tube current to counter the loss of x-ray production efficiency and loss of penetration at lower tube voltages. Despite the disadvantages, symmetric view matching according to the current invention substantially improves streaks and other artifacts due to the view misregistration, sufficient spectrum separation even in a sinusoidal waveform swinging between 80 kV and 135 kV, and contrast-to-noise for the simulated imaging task maximized at monochromatic energy of 75 keV.

State Convergence of Passive Nonlinear Systems With an $L^{2}$ Input

Abstract: We show that the state of a strictly output passive system with an L 2 input converges to zero. The result is applied to the disturbance rejection problem (with reference signal zero), where the disturbance can be decomposed into a finite superposition of sine waves of arbitrary but known frequencies and an L 2 signal. Using an LTI controller, constructed based on the internal model principle, the state trajectories of the plant (and hence also the error signal) converge to zero.

Algorithm for the Nonlinear Propagation of Broadband Jet Noise

Abstract: DOI: 10.2514/1.38122 A frequency-domain algorithm for nonlinear noise propagation is presented. The propagation of noise generated by very high-speed jets exhibits nonlinear effects. This nonlinear behavior, which includes the transfer of energy to high frequencies, is captured in the present algorithm. The generalized nonlinear Burgers equation, which includes atmospheric absorption and dissipation, is solved for the pressure signal in the frequency domain. The results are then obtained as a function of time. A test case of a sinusoidal wave is considered, and the results are compared with the existing analytical Blackstock Bridging Function and Fubini solutions. The predicted results of the sinusoidal wavecaseagreefairlywellwiththeanalyticalresults.JetnoisedatafromtheBoeingLowSpeedAeroacousticFacility are used for the broadband noise prediction. The experimental and predicted power spectral density plots are compared for microphones at different radial locations. The predicted results are in good agreement with the experimental results at all the microphone locations, and the power spectral density plots show a lift at high frequencies due to the nonlinear steepening of the waves. The skewness of the experimental and predicted signal is discussedfortheBoeingdata.Full-scaledataacquiredduringatie-downtestoftheF/A-18Earepropagatedusingthe nonlinear and linear predictions, and the differences in the results are discussed. Ground reflection effects are then presented for both the Boeing and F/A-18E engine data.

CMOS buffer using complementary pair of bulk-driven super source followers

Abstract: A power-efficient rail-to-rail CMOS analogue voltage buffer is presented. It consists of a complementary pair of super source followers, but a bulk-driven input device with the replica-biased scheme is utilised to eliminate the DC level shift, quasi-floating gate transistors to achieve class-AB performance, and a current switch which shifts between the complementary pair to allow rail-to-rail operation. The proposed buffer has been designed for a 0.35 mum CMOS technology to operate at a 1.8 V supply voltage. Simulated results are provided to demonstrate the total harmonic distortion for a 1.6 Vpp 100 kHz sine wave with a 68 pF load is as low as -46 dB, while the static current consumption remains under 8 muA.

Control device for electric rotating machine and method of controlling the machine

Abstract: A control device has a unit for preparing a pattern having first and second periods by comparing a triangular wave and a sine wave having an amplitude ratio set at each value of a modulation factor, and selecting one pattern corresponding to an instructed modulation factor, and a unit for applying a controlled voltage, set at low and high levels in response to first and second periods of the selected pattern, to a generator. The triangular wave has a cycle duration obtained by dividing the cycle duration of the generator by product of 3 and odd number, a crest having a level higher than the sine wave at a timing of each first period, and a trough having a level lower than the sine wave at a timing of each second period.

Enhanced mixing of Newtonian fluids in a stirred vessel using impeller speed modulation

Abstract: This paper reports on an experimental study of mixing intensification using speed modulation of a six-blade Rushton turbine in a stirred vessel. Mixing times were measured using a non-intrusive technique based on direct visualisation of an acid-base reaction in a Newtonian fluid. The impeller speed modulation was achieved by using two waveforms: a square wave and a sine wave. The amplitude was fixed between a maximum Reynolds number of Remax = 60 and minimum Reynolds numbers of Remin = 40 or 30. The wave periods were varied (10, 20, or 40 s) in order to compare the effects of unsteady stirring on mixing performance. It was observed that a square wave protocol with the shortest wave period and the larger amplitude resulted in the shortest time to destroy the observed isolated mixing regions (IMRs), which are known to exist in stirred vessels operating at low Reynolds number. However, the sine wave protocol led to a slow diffusive mechanism in which IMR structures reached an asymptotic volume and remained visible even after several hours. The results are presented and discussed using digital photographs taken at different time intervals during experimentation.

Optimization of powder core inductors of buck-boost converters for Hybrid Electric Vehicles

Abstract: In this paper, the characteristics of Mega-Flux®, JNEX-Core®, amorphous and ferrite cores are compared for the inductor of buck-boost converter for Hybrid Electric Vehicles (HEVs). The core losses are analyzed at the condition of 10kHz sine wave excitations. Permeability fluctuations vs. temperature and magnetizing force will be analyzed and discussed. Under the specifications of buck-boost converter for 20kW THS-II, the power inductor will be designed with Mega-Flux®, JNEX-Core® and the informative simulation results will be provided with respect of dc bias characteristics, core and copper losses.

Operation of a Josephson arbitrary waveform synthesizer with optical data input

Abstract: In order to establish a quantum ac voltage standard at NMIJ/AIST, we have developed a Josephson arbitrary waveform synthesizer based on overdamped Josephson junction arrays (JJAs) using optoelectronics and a liquid helium free compact cryocooler. We have succeeded in the generation of sine waves at 60 Hz and 152.6 kHz. To verify the performance of the system, two different types of JJAs with different characteristic frequencies have been developed. An application to a quantized voltage noise source for Johnson noise thermometry is also discussed, with experimental results.

Sinusoid signal generator for on-chip impedance spectroscopy

Abstract: Compact signal generators are a necessary component for many biomedical and chemical sensor microsystems. This paper presents a signal generator with precise digital frequency control that is 62% smaller the previous designs. The signal generator can produce analog sine waves and digital cosine waves from 4.8 Hz to 39 kHz with a SFDR greater than 99 dB. In a 0.5 µm CMOS process the total signal generator area is 361µm × 1048µm.

Design of on-line UPS based on boost converter

Abstract: Design and build up a new on-line digital UPS based on boost topological structure with a new kind of single-chip computer, STC12C5412AD, realizing sine wave and square wave output, and shifting among 50Hz, 60 Hz, and 400Hz of the supply for adopting into different industrial standards and applications. Such UPS system contains the module of intelligent charging from storage battery and thorough security functions, characterized by the output of un-interruption and high stability, low distortion, free of interference, low cost and multi-function.