The analysis of traveling-wave electrooptic modulator on z-cut and x-cut lithium-niobate substrates is carried out using the finite element method based on a quasi-TEM approximation. The microwave effective index, characteristic impedance, and frequency dependent attenuations are calculated. Optical frequency response is also calculated and hence the bandwidth is estimated for velocity matching and impedance matching conditions. Bandwidth increases significantly for simultaneous velocity and impedance matching but is limited by the microwave losses in the dielectric material. Optical 3-dB bandwidth of more than 140 GHz can be achieved with x-cut LiNbO 3 substrate, when two slots are incorporated in the structure.
Recent energy crisis has forced researchers to design fuel-efficient automobiles, where one of the main critical changes is to reduce aerodynamics drag created by fluid friction. At high speed, aerodynamics drag, especially the pressure drag, creates a substantial backward force, and hence, unwanted excess fuel is consumed to counterbalance this dragging effect, which hinders designing fuel-efficient automobiles. Hence, to mitigate this pressure drag, here in this work, numerical analyses have been done (i) to examine drag coefficient changes through incorporating aerodynamic vents at the front, at the rear, and both front and rear on the automobiles, (ii) to reduce drag force by utilizing exhaust gas to fill the low-pressure vortex, (iii) to investigate the effect of wheels on the overall drag resistance of the model. The ANSYS™ 2020 R1 Fluent module is used to perform this numerical simulation. Appreciable improvement on drag reduction can be found by incorporating above mentioned modifications on racing car body configuration.
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