Design and Development of Non-Linearly Controlled Class-D Audio Amplifier

A systematic and simple approach to develop a 20 W audio frequency range switch mode amplifier is presented in this paper. A non-linear sliding mode (SM) technique-based low cost analog controller enables the realized amplifier to deliver highly linear and efficient operation throughout the audio frequency spectrum. The theoretical aspects and practical limitations in the design and realization of subsystems, such as the signal conditioning stage, power stage and sliding mode controller, are considered, while the viable solution is also stated and justified. The hardware realization scheme is also elaborated, based on which the laboratory prototype is fabricated. Hardware results with a 4 Ω resistive load are given on which the performance of the amplifier is evaluated. The total harmonic distortion (THD) below 1% and 73% efficiency at peak load make the amplifier well suited for high quality audio application.

Sedimentary Setting and Ore-Forming Model in the Songtao Manganese Deposit, Southwestern China: Evidence from Audio-Frequency Magnetotelluric and Gravity Data

The break-up of the supercontinent Rodinia in the late Neoproterozoic led to the formation of the Nanhua rift basin within the South China Block. The Datangpo-type manganese deposit, which developed in the Nanhua rift basin, is one of the most important types of manganese deposits in South China. Although it is widely accepted that deep sedimentary structures significantly affect the manganese ore system, the relationship between the manganese deposits in South China and the Nanhua rifting process is still unclear. The origin of the manganese ore layer remains controversial. In this paper, we integrated the audio-frequency magnetotelluric (AMT) data, gravity data, and comprehensive geological and borehole data analysis to characterize the structure of the Datangpo-type manganese deposit in Songtao, Guizhou Province. The resistivity and density models produced an inclined layered structure, which correlated well with the coeval sediment strata of the Nanhua rift basin. A high-resistivity cap was observed from the surface to a depth of 800 m, corresponding to the Cambrian Loushanguan (ϵ3−4ls) and Palang dolomite formation (ϵ2p), which has helped the storage of the manganese ore. The most significant low-resistivity anomaly (25–40 Ω·m) resides at a depth of 1400 m in the Nantuo (Nh3n) gravel sandstone and Datangpo (Nh2d) silty and carbonaceous shale, corresponding to the ore-forming layer. This distinct low-resistivity layer was possibly produced by aqueous fluids and pyrite in the syn-sedimentary fault and alteration zone. The accumulations of sulfide minerals in the rock samples suggest a possible anoxic-euxinic deposition environment during the manganese mineralization and precipitation. The fault revealed in the resistivity models is perhaps a previous fault zone produced by extension in the Nanhua rifting process, which provided migration and upwelling channels for ore-forming minerals. Based on our resistivity models, density models, and geological survey, the manganese ore-forming model was derived, which can help to provide geophysical evidence for the origin of the Datangpo-type manganese deposit.

Optimal Transceiver Distance of Controlled-source Audio-frequency Magnetotelluric Sounding Method

Currently, the use of Cagniard apparent resistivity and phase is still the main method and means to process and interpret controlled-source audio-frequency magnetotelluric (CSAMT) sounding data. The CSAMT data must meet the conditions in the far zone to use the magnetotelluric (MT) sounding inversion interpretation method. The conditions in the far zone are directly related to transceiver distance; Hence, the distance measured by the CSAMT method is directly related to the reliability and credibility of the data. In this study, based on the formation wave and ground wave of the analytical expression for the electric field in a uniform half-space condition, the response laws of the formation wave and the ground wave are analyzed. After rigorous mathematical derivation, the formula for determining the optimal transceiver distance of the CSAMT is obtained, and the steps for using this formula in practical application are given. The actual field application verifies the rationality of the derived formula. This study provides a reference for the design of a CSAMT field source, and effectively guides the determination of CSAMT transceiver distance in the field.

Frequencies 171.160 Hz, 174.989 Hz, and 1185.131 Hz useful in combating COVID-19 (Novel Coronavirus)

The paper presents the works carried out by different researchers for identifying the SARS-CoV-2 virus structure, and its background with the present medication being addressed to the COVID-19 patients. The paper discusses three candidates for possible defense and cure of humans against the virus along with the regular medication. The first is the resonant frequency therapy, which has proven its efficacy for treating different types of viral infection and cancer cells as the capsid of Rubella measles virus, Satellite Tobacco necrosis Virus, Cancer cells and many more are neutralized on the application of frequency equal to the resonance frequency of the protein shell of the virus. It is expected that there must be a resonance frequency corresponding to the capsid of the SARS-CoV-2, on the application of which might result in the disintegration of the protein shell. As treating a huge number of people in hospitals is becoming increasingly difficult and large number of population is under quarantine, a resonance audio frequency of this sort embedded in a soothing music can be melodius, and the same if played in public spaces and homes might help a great deal. The frequencies (approximate values) are 171.160 Hz, 174.989 Hz, 1185.131 Hz the complete details regarding administration and calculation of the frequencies are discussed in this manuscript. This treatment along with the presently administered treatment to COVID-19 patients might aid in their quick recovery from illness. Further the audio frequency/ resonance frequency therapy, and the strategy discussed in this manuscript might be useful in future from any kind of Virus attacks/ Biological warfares either intentionally or naturally. Also, the medicinal properties of ethnomedical plants such as Piper nigrum, and Ocimum tenuiflorum L and essential oils such as Eucalyptus oil are discussed. The last one being the antiviral activities of copper in the form of copper oxide nanoparticles in medicine which has proven its efficacy for viral prevention, replication, and RNA degradation are also discussed.