Model modification and feature study of Duffing oscillator

With the development of chaos theory, Duffing oscillator has been extensively studied in many fields, especially in electronic signal processing. As a nonlinear oscillator, Duffing oscillator is more complicated in terms of equations or circuit analysis. In order to facilitate the analysis of its characteristics, the study analyzes the circuit from the perspective of vibrational science and energetics. The classic Holmes-Duffing model is first modified to make it more popular and concise, and then the model feasibility is confirmed by a series of rigorous derivations. According to experiments, the influence of driving force amplitude, frequency, and initial value on the system is finally explained by the basic theories of physics. Through this work, people can understand the mechanisms and characteristics of Duffing oscillator more intuitively and comprehensively. It provides a new idea for the study of Duffing oscillators and more.

OPTOELECTRONIC DEVICE FOR MEASURING THE POWER OF LASER RADIATION

A device for measuring the power of the laser radiation.has been designed. The device consists of transmitter and receiving part. The transmitter includes optical radiation source and optical system for collimation of radiation. The receiver part consists of silicon photodiodes, electronic signal processing unit and unit for measurements.

Electrical tunability of terahertz nonlinearity in graphene

Graphene is conceivably the most nonlinear optoelectronic material we know. Its nonlinear optical coefficients in the terahertz frequency range surpass those of other materials by many orders of magnitude. Here, we show that the terahertz nonlinearity of graphene, both for ultrashort single-cycle and quasi-monochromatic multicycle input terahertz signals, can be efficiently controlled using electrical gating, with gating voltages as low as a few volts. For example, optimal electrical gating enhances the power conversion efficiency in terahertz third-harmonic generation in graphene by about two orders of magnitude. Our experimental results are in quantitative agreement with a physical model of the graphene nonlinearity, describing the time-dependent thermodynamic balance maintained within the electronic population of graphene during interaction with ultrafast electric fields. Our results can serve as a basis for straightforward and accurate design of devices and applications for efficient electronic signal processing in graphene at ultrahigh frequencies.

The Voice

Voice and singing are fundamental to music. Scales and content reflect our personal culture. Something beautiful and inspiring to one person may be a boring cacophony to another. Viewing musical evolution from the perspective of culture is therefore varied and individual. Input from science is generally less obvious, except for changes generated from acoustics of buildings, broadcasting, and electronic sound equipment. Medical studies reveal how we form sounds and tone quality, and modern electronic signal processing shows the complexity of the harmonic content of singing. The changes between sweetness, harshness, carrying power, and so on, all depend on not just volume, but the fundamental note and its harmonics, plus all the other frequencies generated in our vocalization. One fundamental may have 50 or more other frequencies. This signal processing tool is invaluable for understanding voice production.

ESPECIALLY THE MATHEMATICAL DESCRIPTION OF RANDOM SIGNALS WITH THREE LEVELS OF QUANTIZATION

The article describes the method of mathematical description of an additive mixture signal with noise when using the three‑level quantization. Method is based on the presentation of the implementation of the signal after quantization in the form of a random discrete 3D vector. It is proposed that statistical calculation technique characteristics of three‑level signals. The technique allows visualizing the probability distribution law of radar signals of different shapes on the background noise and calculating its numeric parameters. Knowledge of the law of probability distributions, assuming that the only inlet noise and distribution law of probability signal with noise allows to calculate the detection quality indicators to build a detector performance. Three‑level quantization allows to considerably simplify the technical implementation of electronic signal processing device with acceptable energy loss.

Recent Advances in Cast Iron Structure and Properties Ultrasonic Testing and Flaw Detection

The advantage of ultrasonic testing of iron castings prior to destructive control consists of an impressive reduction in time and costs, as well as the ability to assess the quality of the metal anywhere on the castings. According to the acoustic characteristics of cast iron it is possible to determine the form of graphite in it and its strength. The presence of chill in the metallic base and the thickness of the chilled layer is also determined by ultrasonic method. The use of electronic signal processing allows to distinguish it from high structural noise, which makes possible the testing of cast iron for a thickness of several meters. The use of transducers with phased array is the basis of the flaw detection of containers for nuclear waste from cast iron with globular graphite with a thickness of 500 mm.