Pandemics, Delays, and Pure Data: on ‘afterlives’ (2020), for Flute and Live Electronics and Visuals

The essay addresses creative and technical aspects of the piece ‘afterlives’ (2020), for flute and live electronics and visuals. Composed and premiered in the context of the COVID-19 pandemic, the composition employs audiovisual processes based on different audiovisual techniques: phase-vocoders, buffer-based granulations, Ambisonics spatialization, and variable delay of video streams. The resulting sounds and images allude to typical situations of social interaction via video conferencing applications. ‘Afterlives’ relies on an interplay between current, almost-current, and past moments of the audiovisual streams, which dephase the performer’s images and sounds. I have avoided, in text, delving deeper into the Pure Data abstractions and or into the musical analysis of my composition. The main purpose of the text is rather to present compositional/technical elements of ‘afterlives’ and discuss how they enable new experiences of time.

Two Year Cosmology Large Angular Scale Surveyor (CLASS) Observations: Long Timescale Stability Achieved with a Front-end Variable-delay Polarization Modulator at 40 GHz

The Cosmology Large Angular Scale Surveyor (CLASS) is a four-telescope array observing the largest angular scales (2≲ ℓ ≲ 200) of the cosmic microwave background (CMB) polarization. These scales encode information about reionization and inflation during the early universe. The instrument stability necessary to observe these angular scales from the ground is achieved through the use of a variable-delay polarization modulator as the first optical element in each of the CLASS telescopes. Here, we develop a demodulation scheme used to extract the polarization timestreams from the CLASS data and apply this method to selected data from the first 2 yr of observations by the 40 GHz CLASS telescope. These timestreams are used to measure the 1/f noise and temperature-to-polarization (T → P) leakage present in the CLASS data. We find a median knee frequency for the pair-differenced demodulated linear polarization of 15.12 mHz and a T → P leakage of <3.8 × 10−4 (95% confidence) across the focal plane. We examine the sources of 1/f noise present in the data and find the component of 1/f due to atmospheric precipitable water vapor (PWV) has an amplitude of 203 ± 12 μ K RJ s for 1 mm of PWV when evaluated at 10 mHz; accounting for ∼17% of the 1/f noise in the central pixels of the focal plane. The low levels of T → P leakage and 1/f noise achieved through the use of a front-end polarization modulator are requirements for observing of the largest angular scales of the CMB polarization by the CLASS telescopes.

Mixed Caputo Fractional Neutral Stochastic Differential Equations with Impulses and Variable Delay

In this manuscript, a new class of impulsive fractional Caputo neutral stochastic differential equations with variable delay (IFNSDEs, in short) perturbed by fractional Brownain motion (fBm) and Poisson jumps was studied. We utilized the Carathéodory approximation approach and stochastic calculus to present the existence and uniqueness theorem of the stochastic system under Carathéodory-type conditions with Lipschitz and non-Lipschitz conditions as special cases. Some existing results are generalized and enhanced. Finally, an application is offered to illustrate the obtained theoretical results.

Measurements of the local temperature correlation time in a turbulent flame using coherent anti-Stokes Raman spectroscopy

The feasibility to determine the timescale of pulsations of “instantaneous” local temperatures in a turbulent flame at a microsecond time scale by using coherent anti-Stokes Raman scattering (CARS) spectroscopy is demonstrated for the first time to our knowledge. A laboratory laser measurement complex was utilized, based on two CARS-spectrometers employing synchronized pulse-repetitive lasers with 10 ns pulse duration. The system enabled to record, with high temporal resolution (in one single laser shot) and at a variable delay between two sequential shots following each other in pairs at a repetition rate of 10 Hz, series of CARS spectra of N2 molecules from a probe volume as small as 0.03×0.03×2 mm3. From the spectra, “instantaneous” temperatures at a given delay were derived. The obtained values enabled calculation of the correlation coefficient of temperature pulsations vs the delay. The results are presented for the series of 500 single-shot coupled measurements, at the delays in the range 1 μs – 0 ms, of local gas temperatures in a few points of an open turbulent partially premixed methane-air flame of a model burner with visually distinguishable stability of combustion. The average temperatures were between 1500 K and 1800 K. The measurements allowed temperature correlation times in the selected points of the flame to be derived.

Study on the Lyapunov Stability of a Time-Discrete Macro Traffic System with Variable Delay and Feedback Control

This paper constructs and analyzes a time-discrete macro traffic system with bounded variable delay and feedback control strategy. By theoretical analysis using the Lyapunov theorem, a stable condition of the macro traffic system is derived under which traffic jams can be suppressed. The traffic developing properties of the new traffic system for different variable delay and feedback control parameters are illustrated through simulation. The results show that variable delay can easily lead a traffic system to evolve into a traffic jam, and the feedback control strategy can enhance the stability of the traffic system with respect to variable delay. Moreover, the traffic unstable level caused by variable delay is less than the unstable extent caused by the constant upper bound of variable delay; still it is more serious than the traffic fluctuation caused by the constant lower bound of variable delay.