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Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
aperiodic convolution the convolution of two sequences. See convolution. aperiodic signal a signal that is not periodic, i.e., one for which x(t) = x(t + T ). This means that the signal x(t) has a property that is changed by a time shift T . See also periodic signal. aperiodic waveform this phrase is used to describe a waveform that does not repeat itself in a uniform, periodic manner. Compare with periodic waveform. aperture (1) an opening to a cavity, or waveguide, from which radiation is either received or transmitted. Typically used as antenna or a coupling element. (2) a physical space available for beam to occupy in a device. Aperture limitations are the physical size of the vacuum chamber, a magnetic field anomaly may deflect the beam so that the full available aperture cannot be used. aperture antenna an antenna with a physical opening, hole, or slit. Contrast with a wire antenna. aperture correction signal compensation used to correct the distortion caused by the non-zero aperture of a scanning electron beam. A standardized measure of the selectivity of a circuit or system. The -3 dB (or half-power) band width
Contribution of Microgrids to the Development of the Smart Grid
Published in David Bakken, Krzysztof Iniewski, Smart Grids, 2017
Tine L. Vandoorn, Lieven Vandevelde
The VBD control of [44] is a variant of the P/V droop control that focuses on the optimal integration of renewables in the network and also incorporates a direct current (dc)-bus controller. In the VBD control, the P/V droop controller is divided into two droop controllers, and constant-power bands are included, as depicted in Figure 9.3. Further details of these control loops are given in [44]. The parameter 2b determines the width of the constant-power band. When the terminal voltage of the DG unit is in the constant-power band, that is, (1−b)Vg,ref<Vg<(1+b)Vg,ref, the DG unit delivers its reference power. Otherwise, the power of the DG unit is changed. A distinction is made between dispatchable and less dispatchable DG units.
UAS Airframe and Powerplant Design
Published in Douglas M. Marshall, R. Kurt Barnhart, Eric Shappee, Michael Most, Introduction to Unmanned Aircraft Systems, 2016
Four-stroke motors can afford certain design benefits: less vibration (in comparison to a two-stroke engine), quieter operation, relatively high torque, and a broader power band. Where range and endurance are important factors in the anticipated mission of the UAS, four-stroke engines offer the major advantage of providing the highest fuel efficiency of any internal combustion engine. On the other hand, they are also generally heavier, more complex, and expensive and do not, in comparison to other powerplants (e.g., two-cycle engines), commonly power unmanned aircraft. One example of a UAS four-stroke powerplant would be the 120 horsepower (hp) Teledyne Continental IO-240-B7B installed on the Eagle ARV UAS. Another is the Austrian-produced, (opposed) four cylinder, 115 hp, turbocharged Rotax 914F engine that powers the RQ/MQ-1 Predator A. The IAI RQ-5 Hunter was also powered by a Moto Guzzi two cylinder, four-stroke powerplant. Small four stroke engines, available in sizes of 7.5 cc’s and above, may be installed on sUAS platforms. An example would be the Barnard Microsystems InView UAS powered by a pair of 29.1 cc (1.8 cubic inch) displacement powerplants that burn 100 low lead aviation fuel to which is added synthetic oil in a 20:1 ratio to provide lubrication.
Electroencephalogram-based cognitive load level classification using wavelet decomposition and support vector machine
Published in Brain-Computer Interfaces, 2023
Farzana Khanam, A.B.M. Aowlad Hossain, Mohiuddin Ahmad
Table 2 depicts the comparison among the signal powers as the corresponding five features regarding n-back tasks. The evaluation result is based on the selected four channels of a random subject. The channels are AFz, Cz, Pz and POz. From Table 2, we can see that there are significant variations among relative power bands according to the features of different task levels among these channels. The value of the power band increases accordingly to the order of selected DC whereas AC shows maximum power for these channels. However, we cannot conclude any fixed pattern following the results. To understand a clear pattern of the variation of signal power due to different cognitive loads, signal power variations of all channels are supposed to be presented. For this reason, the changes in the power value of all channels are separately presented by topographs in Figure 7. These topographs are prepared from the average signal power of all trials of randomly chosen participant data. Figure 7(a), Figure 7(b), and Figure 7(c) are representing the topography of 0-back, 2-back, and 3-back cognitive load, respectively.
Electronically Tunable Grounded Capacitance Multiplier
Published in IETE Journal of Research, 2022
Shashwat Singh, Neeta Pandey, Rajeshwari Pandey
To validate the performance of the presented capacitance multiplier using CCIIITA, a low power band reject filter is implemented. The capacitor C of the notch filter, shown in Figure 14, is replaced by the presented capacitance multiplier circuit. A total multiplication factor of 50 is achieved by utilizing the presented multiplier circuit. Passive component values for the notch filter are given in Table 6. The values of capacitor portray that it can be integrated. The simulation results verify that the presented capacitance multiplier shows decent performance. The transfer function of the notch filter is given by
Fatigue failure of pb-free electronic packages under random vibration loads
Published in International Journal for Computational Methods in Engineering Science and Mechanics, 2018
Saravanan S., Prabhu S., Muthukumar R., Gowtham Raj S., Arun Veerabagu S.
The damping ratio ζ is calculated from the measured FRF using half power band width method. According to this technique [17], the damping ratio ζ is given by the expression where ω1, ω2 are frequencies at which the magnitude of the frequency response curve is (1/√2) times the peak response obtained at the natural frequency ωr. The half power bandwidth for the first natural frequency is shown in Fig. 8. The calculated damping ratio for the fundamental natural frequency is 0.0155.