Sine wave

About: Sine wave is a research topic. Over the lifetime, 12183 publications have been published within this topic receiving 93013 citations. The topic is also known as: sinusoid.

Modulation method for a multiple drive system based on a two-stage direct power conversion topology with reduced input current ripple

Abstract: A new two-stage multi-drive direct power conversion (DPC) topology suited for multi-drive application is proposed, having an input port for a three-phase power supply and several output ports to connect three-phase loads, which are independently controlled and allow for sine wave in-sine wave out operation. This is a cost effective topology compared to a standard matrix converter because the multiple three-phase loads share the cost of the controlled rectification stage. A new method to reduce the high frequency ripple from the input current is also proposed based on interleaving the switching patterns of the inversion stages, which have to form two groups, allowing for size reduction of the input current filter. This is validated by experiments on a realistic laboratory prototype, while its limitations are determined by simulations.

A study of sine-wave contrast sensitivity by two psychophysical methods

Abstract: In the literature on visual contrast thresholds for sine wave gratings, little attention has been paid to the psychophysical methods used to obtain these spatial-frequency response curves. Here we report a comparison of such data obtained by two quite different psychophysical methods, but otherwise under identical conditions, using five Ss. Both experiments were run by computer: (1) In the method of adjustments, the computer program merely controls the order of the stimuli and records S’s contrast settings. (2) In the forced-choice staircase (FCS) technique, the program determines how often S can discriminate the sinusoidal grating from a uniform field, informs S of his accuracy, controls the stimulus contrast on the basis of S’s preceding responses, and brackets his threshold by a series of successive approximations. Method 2 eliminates criterion effects that occur in Method 1, and hence tends to minimize individual differences. However, the FCS technique requires an order of magnitude more observing time to obtain equally smooth contrast sensitivity curves. FCS also increases the/overall sensitivity of some Ss by as much as five times, but it does not significantly change theshape of the contrast sensitivity curve; both methods show strong effects of lateral inhibition at low spatial frequencies.

Apparatus and method for phase resolved fluorescence lifetimes of independent and varying amplitude pulses

Abstract: A flow cytometer measures phase fluorescence lifetimes by the phase shift of a reference signal and an emission from a particle or cell in a flow chamber (17). An acoustic optic modulator (13) modulates laser light with a sinusoidal wave of a predetermined frequency to excite particles or cells. Detectors respond to emissions of individual particles or cells in the form of an output signal pulse at the predetermined frequency. The output signal pulse is divided into equal pulses with each at the modulation frequency, the same amplitude and fidelity and amplitude. One part of the divided pulse is stripped of its envelope to pass the width thereof and out of band components are rejected. A variable amplifier passes a portion of the pulse above a preset level. A delay line sets a central part of the signal at a predetermined point in time. A circuit limits the attenuated one part. A double balance mixer multiplies and the relates the limited signal with a reference signal to determine the phase shift. The next step attenuates the signal to a preset level so it can be limited, then filtered to remove harmonics above the modulation frequency and an envelope below. A double balance mixer multiplies the limited signal with a reference signal and produces a multiple signal and determining the relative phase shift of the emissions.

The Size-Dependent Thermoelastic Vibrations of Nanobeams Subjected to Harmonic Excitation and Rectified Sine Wave Heating

Abstract: In this article, a nonlocal thermoelastic model that illustrates the vibrations of nanobeams is introduced. Based on the nonlocal elasticity theory proposed by Eringen and generalized thermoelasticity, the equations that govern the nonlocal nanobeams are derived. The structure of the nanobeam is under a harmonic external force and temperature change in the form of rectified sine wave heating. The nonlocal model includes the nonlocal parameter (length-scale) that can have the effect of the small-scale. Utilizing the technique of Laplace transform, the analytical expressions for the studied fields are reached. The effects of angular frequency and nonlocal parameters, as well as the external excitation on the response of the nanobeam are carefully examined. It is found that length-scale and external force have significant effects on the variation of the distributions of the physical variables. Some of the obtained numerical results are compared with the known literature, in which they are well proven. It is hoped that the obtained results will be valuable in micro/nano electro-mechanical systems, especially in the manufacture and design of actuators and electro-elastic sensors.

A fast, two-point, three-dimensional raytracing algorithm using a simple step search method

Abstract: The simplex method of function minimization is used to find the ray that follows the path of minimum time through an arbitrary three-dimensionally varying medium. The advantage of this method is that it is extremely fast, always converges, and lends itself to a variety of velocity parameterizations. The first step in the algorithm is to find the minimum time circular arc path between the source and receiver using an exhaustive search method. Then perturbations, consisting of a sum of N sine wave harmonics with their zero crossings at the endpoints, are made to the circular arc path. The simplex method searches for the amplitude coefficients that produce the path of least time. On a VAX-750 running the VMS operating system, the first arriving ray for a station receiver distance of 96 km is computed to an accuracy of 0.02 sec, computed in a southern California velocity structure using less than 26 sec of computer time. The required computer time decreases as the ray path distance decreases.