CFD-CAA Method for Prediction of Pseudosound and Emitted Noise in Quadcopter Propeller

Subsonic flow air blade machines like UAV propellers generate intensive noise thus the prediction of acoustic impact, optimization of these machines in order to reduce the level of emitted noise is an urgent engineering task. Currently, the development of calculation methods for determining the amplitudes of pressure pulsations and noise characteristics by CFD-CAA methods is a necessary requirement for the development of computer-aided design methods for blade machines, where the determining factors are the accuracy and speed of calculations. The main objective is to provide industrial computer-aided design systems with a highly efficient domestic software to create optimal designs of UAV blade machines that provide a given level of pressure pulsations in the flow part and radiated noise. It comprises: 1) creation of a method for the numerical simulation of sound generation using the correct decomposition of the initial equations of hydrodynamics of a compressible medium and the selection of the source of sound waves in a three-dimensional definition, taking into account the rotation of blades and their interaction with the stator part of the UAV; 2) decomposition of the boundary conditions accounting pseudo-sound disturbances and the complex acoustic impedance at the boundaries of the computational domain 3) development of an effective SLAE solver for solving the acoustic-vortex equation in complex arithmetic (taking into account the boundary conditions in the form of complex acoustic impedance); 4) testing of a new method at all stages of development using experimental data on the generation of pressure pulsations and aerodynamic noise, including a propeller noise measurements.

Spatial and temporal variation of the ambient noise environment of the Sikkim Himalaya

Ambient noise characteristics are perused to assess the station performance of 27 newly constructed broadband seismic stations across Sikkim Himalaya and adjoining Himalayan foreland basin, installed to study the seismogenesis and subsurface structure of the region. Power spectral densities obtained at each station, compared against the global noise limits, reveal that observed vertical component noise levels are within the defined global limits. However, the horizontal components marginally overshoot the limits due to the tilt effect. Ambient noise conditions significantly vary with different installation techniques, analysis revealing that seismic sensors buried directly in the ground have reduced long-period noise in comparison to pier installations. Tectonic settings and anthropogenic activities are also noted to cause a significant rise across short-period and microseism noise spectrum, varying spatially and temporally across the region. Day-time records higher cultural noise than night-time, while the microseism noise dominates during the monsoonal season. An assessment of the effect of the nationwide lockdown imposed due to COVID-19 pandemic revealed a significant decrease in the short-period noise levels at stations installed across the foreland basin marked with higher anthropogenic activity. Our study summarizes the overall ambient noise patterns, validating the stability and performance of the seismic stations across the Sikkim Himalayas.

Investigation of random telegraph noise characteristics of Hf-based MONOS nonvolatile memory devices with HfO2 and HfON tunneling layer

This paper investigated the low frequency noise (LFN) utilizing 1/f noise and random telegraph noise (RTN) characteristics of Hf-based metal/oxide/nitride/oxide/silicon (MONOS) nonvolatile memory (NVM) device with HfO2 and HfON tunneling layer (TL). The low frequency noise spectral density (SID ) was investigated to evaluate the interface characteristics with fresh and after programming/erasing (P/E) cycles of 104. Both devices show similar slope of ~1/f in all of the frequency regions. Although HfON TL shows high SID compared to HfO2 TL, increased ratio is 15.4 which is low compared to HfO2 TL of 21.3. As decreasing the channel length from 10 to 2 μm, HfON TL shows small increased ratio of SID . Due to the nitrided characteristics, HfON TL suppress the degradation of interface. Finally, it is found that trap site of HfO2 TL is located near the interface by RTN measurement with capture (τC) and emission time constant (τE).

Effect of intensity and duration of anthropic noises on European mink locomotor activity and faecal cortisol metabolite levels

Human activities involving noise emission can affect wild animals. European mink was exposed to road noise and human voice playbacks to analyse how sound intensity level and duration of both noises altered the time that individuals were active and if their faecal cortisol metabolite (FCM) levels varied. A Hierarchical Analysis Cluster was performed to established two mink groups with respect to both noise source type: short duration/low intensity (SL) and long duration/high intensity (LH). We performed General Linear Mixed Models to evaluate the variation in locomotor activity duration (s) and FCM (ng/g) levels, respectively. The results showed both road noise and human voices decreased locomotor activity duration in SL more sharply compared to LH, and human voices were the triggers that induced the most pronounced response to both exposure conditions. FCM levels increased in SL compared to LH during road noise while the opposite happened during human voices. Differences based on sex and age of individuals were observed. In conclusion, noise characteristics given by the sound type determined the variations in locomotor activity duration while noise exposure level determined the variations in FCM levels. Attention should be paid to noisy activities (e.g. recreational activities for visitors in protected natural areas) and loud groups of people to conserve wildlife, especially noise sensitive species.

A large gain variable range, high linearity, lownoise, low DC offset VGAs used in BD system

In this paper, a large gain variable range, high linearity, low noise, low DC offset VGAs with a simple gain-dB variable circuit are introduced. In the VGAs chain, the last and the first VGAs employ Bipolar transistors, to improve the linearity and noise characteristics. And the middle three stages VGAs employ MOS transistors. The whole circuitry is designed in 0.35um BiCMOS process, including variable gain amplifiers (VGAs) , fixed gain amplifiers , gain control and DC offset cancellation parts. The automatic gain control loop (AGC) provides a process independent gain variable range of 60dB (including 50dB gain-dB-linearity variable range), with a 200us loop lock time, the VGAs provide a 73dB largest gain, the THD is less than 1% at a 1V(P-P) output level; the equivalent output integral noise is 0.011v/√hz@20MHz bandwidth. The whole area is 1173um*494 um, and the power is 7.1mA at 3.3V signal supply voltage.

Preliminary analysis on the noise characteristics of MWISP data

Noise is a significant part within a millimeter-wave molecular line datacube. Analyzing the noise improves our understanding of noise characteristics, and further contributes to scientific discoveries. We measure the noise level of a single datacube from MWISP and perform statistical analyses. We identified major factors which increase the noise level of a single datacube, including bad channels, edge effects, baseline distortion and line contamination. Cleaning algorithms are applied to remove or reduce these noise components. As a result, we obtained the cleaned datacube in which noise follows a positively skewed normal distribution. We further analyzed the noise structure distribution of a 3D mosaicked datacube in the range l = 40 ⋅ ° 7 to 43 ⋅ ° 3 and b = − 2 ⋅ ° 3 to 0 ⋅ ° 3 and found that noise in the final mosaicked datacube is mainly characterized by noise fluctuation among the cells.