High Lift Device Modifications for Reducing Airport Noise - A Review

Aircraft noise has been one of the top environmental issues at and near airports across the country because of its negative impact on communities. The growth of the nation's air transportation system is restricted predominantly due to regulations on limiting aircraft noise generated around airports. Reducing aircraft noise will lead to wider community acceptance of new or larger airports, lower airline operating costs by reducing noise quota fees, and increase air traffic growth through operating more flights. One of the most significant contributors to aircraft noise, structural vibrations caused by air flow across its frame, are high lift devices. A review of high lift devices, such as flaps, and methods to reduce their noise levels will be presented. Solution reviews will focus on reducing flap trailing-edge scattering and flap side-edge vortices.

Edge scattering limited crosstalk analysis in adjacent multilayer graphene interconnects and its impact on gate oxide reliability

Purpose This paper aims to present the edge scattering dominant circuit modeling. The effect of crosstalk on gate oxide reliability (GOR), along with the mitigation using shielding technique is further studied. Design/methodology/approach An equivalent distributed Resistance Inductance Capacitance circuit of capacitively coupled interconnects of multilayer graphene nanoribbon (MLGNR) has been considered for T Simulation Program with Integrated Circuit Emphasis (TSPICE) simulations under functional and dynamic switching conditions. Complementary metal oxide semiconductor driver transistors are modeled by high performance predictive technology model that drive the distributed segment with a capacitive load of 0.001 fF, VDD and clock frequency as 0.7 V and 0.2 GHz, respectively, at 14 nm technology node. Findings The results reveal that the crosstalk induced delay and noise area are dominated by the overall mean free path (MFP) (i.e. including the effect of edge roughness induced scattering), in contrary to, acoustic and optical scattering limited MFP with the temperature, width and length variations. Further, GOR, estimated in terms of average failure rate (AFR), shows that the shielding technique is an effective method to minimize the relative GOR failure rate by, 0.93e-7 and 0.7e-7, in comparison to the non-shielded case with variations in interconnect’s length and width, respectively. Originality/value Considering realistic circuit modeling for MLGNR interconnects by incorporating the edge roughness induced scattering mechanism, the outcomes exhibit more penalty in terms of crosstalk induced noise area and delay. The shielding technique is found to be an effective mitigating technique for minimizing AFR in coupled MLGNR interconnects.

Influence of the liner-type treatment on the trailing-edge noise generated by a flat plate

Several liner-type treatments (three different rectangular grooves covered by three different low porosity wire-mesh screens) on the trailing edge of a flat plate have been investigated in the anechoic wind-tunnel of Université de Sherbrooke. Far-field acoustic directivity measurements have been achieved at Reynolds numbers based on the plate length from [Formula: see text] to [Formula: see text], yielding radiation maps of all possible liner combinations that are then compared to the reference solid flat plate and to the plate with inserts alone. Noise from the flat plate corresponds to dipolar trailing-edge scattering with an extra shallow hump attributed to the unsteady flow recirculation behind the thick plate. When grooves are added, the latter contribution is amplified and additional cavity noise is observed with several tones and humps. The tones are shown to be resonance between high order modified Rossiter modes and cavity depthwise modes. The hump is a combination of drag dipoles and cavity monopoles from the groove row. The addition of screens always reduces the amplification of the dipolar edge scattering but exhibits very different non-linear responses for the cavity noise. The combination screen with the smallest cells and the insert with the shallowest cavities (corresponding to the same type of treatment applied previously on the Controlled-Diffusion airfoil) yields the lowest levels overall, while the screen with intermediate cell size almost always triggers noise amplification and the screen with a coarse mesh has an intermediate behavior. At high frequencies, the previously reported roughness noise is also observed.

Design of Tapered Periodic Meta-Surfaces for Suppressing Edge Electromagnetic Scattering

In this paper, a novel approach for designing tapered periodic meta-surfaces (TPMS) is proposed for suppressing electromagnetic scattering from a trailing edge of a square metallic plate with a given thickness. The TPMS is realized by periodic square metallic patches with tapered dimensions at the direction perpendicular to the considered edge but keeping its period unchanged. Based on the geometric phase interaction, the mechanism of suppressing electromagnetic scattering is analyzed. The lossy material is not required in this design, so it doesn’t generate thermal energy and benefits infrared stealth of military objects. The backscattering properties from the trailing edge with the proposed TPMS loading are analyzed and compared with that of original trailing edge. It is observed that wide angular trailing edge scattering suppressing can be obtained and the average value of mono-static radar cross section (RCS) reduction is 10 dB for L-band, S-band and C-band. Finally, the bi-static RCS properties and energy distribution of the proposed structure are also proposed to explain the mechanism of the electromagnetic scattering suppression of the trailing edge employed with the TPMS.

Graphene transistor based on tunable Dirac fermion optics

We present a quantum switch based on analogous Dirac fermion optics (DFO), in which the angle dependence of Klein tunneling is explicitly utilized to build tunable collimators and reflectors for the quantum wave function of Dirac fermions. We employ a dual-source design with a single flat reflector, which minimizes diffusive edge scattering and suppresses the background incoherent transmission. Our gate-tunable collimator–reflector device design enables the quantitative measurement of the net DFO contribution in the switching device operation. We obtain a full set of transmission coefficients between multiple leads of the device, separating the classical contribution from the coherent transport contribution. The DFO behavior demonstrated in this work requires no explicit energy gap. We demonstrate its robustness against thermal fluctuations up to 230 K and large bias current density up to 102A/m, over a wide range of carrier densities. The characterizable and tunable optical components (collimator–reflector) coupled with the conjugated source electrodes developed in this work provide essential building blocks toward more advanced DFO circuits such as quantum interferometers. The capability of building optical circuit analogies at a microscopic scale with highly tunable electron wavelength paves a path toward highly integrated and electrically tunable electron-optical components and circuits.

A Comparison Between Edge Neighbor Rupture Degree and Edge Scattering Number in Graphs

The vulnerability measure of a graph or a network depends on robustness of the remained graph, after being exposed to any intervention or attack. In this paper, we consider two edge vulnerability parameters that are the edge neighbor rupture degree and the edge scattering number. The values of these parameters of some specific graphs and their graph operations are calculated. Thus, we analyze and compare which parameter is distinctive for the different type of graphs by using tables.