Potential Intensification Rate of Tropical Cyclones in a Simplified Energetically Based Dynamical System Model: An Observational Analysis

In a recent study by Wang et al. (2021a) that introduced a dynamical efficiency to the intensification potential of a tropical cyclone (TC) system, a simplified energetically based dynamical system (EBDS) model was shown to be able to capture the intensity-dependence of TC potential intensification rate (PIR) in both idealized numerical simulations and observations. Although the EBDS model can capture the intensity-dependence of TC intensification as in observations, a detailed evaluation has not yet been done. This study provides an evaluation of the EBDS model in reproducing the intensity-dependent feature of the observed TC PIR based on the best-track data for TCs over the North Atlantic, central, eastern and western North Pacific during 1982–2019. Results show that the theoretical PIR estimated by the EBDS model can capture basic features of the observed PIR reasonably well. The TC PIR in the best-track data increases with increasing relative TC intensity (intensity normalized by its corresponding maximum potential intensity–MPI) and reaches a maximum at an intermediate relative intensity around 0.6, and then decreases with increasing relative intensity to zero as the TC approaches its MPI, as in idealized numerical simulations. Results also show that the PIR for a given relative intensity increases with the increasing MPI and thus increasing sea surface temperature, which is also consistent with the theoretical PIR implied by the EBDS model. In addition, future directions to include environmental effects and make the EBDS model applicable to predict intensity change of real TCs are also discussed.

GAS TEMPERATURE MEASUREMENT IN THE ACTIVE ZONE OF STREAMER DISCHARGE UNDER DIFFERENT APPLIED VOLTAGES

The experimental results on the gas temperature measurement in the active zone of streamer discharge in air at the atmospheric pressure are presented. The gas temperature value was obtained by the optical method for measur-ing the relative intensity of the rotational lines for the radiation of the second positive (II+) system of molecular ni-trogen, transition bands (С3Пu(0)→B3Пg(0)). It was found that in discharge gap d = 8 mm, depending on the ap-plied voltage (in the range of 6.1…7.8 kV with a step of 0.2 kV), the gas temperature varied from 609 to739 K. The unevenness of the gas temperature change in the active zone of discharge with the increase in the applied voltage is shown. This may be related to the possible changes in the rotational state of nitrogen molecules upon excitation of their electronic state by electrons.

Multi-wavelength achromatic bifocal metalenses with controllable polarization-dependent functions for switchable focusing intensity

In this paper, bifocal metalens are designed through simultaneously controlling two polarization-dependent functions, which can respectively focus x-polarized and y-polarized light into different positions, and the relative intensity between two foci can be continuously tuned through a simple rotation of the incident linear polarization direction. The proposed metalenses are composed of rectangle nanopillars with spatially varying widths and lengths, which provide distinct propagating phases under two orthogonal polarizations. Therefore, there exists a freedom of degree to achieve two polarization-dependent focusing functions. More importantly, these nanopillars possess the excellent dispersion engineering, and provide an effective way for the realization of achromatic bifocal metalenses. After powerful optimizations, two achromatic bifocal metalenses are constructed and further demonstrated numerically. The x-polarized and y-polarized components are focused into different positions under different working wavelengths. Simulated results agree well with our designs. The approach here is expected to find optical applications in micro-manipulation, optical communication and multicolor display.

Intensity noise characteristics of intracavity contacted VCSELs with rhomboidal oxide current aperture for the magnetometric sensor with Cs133 vapor cell used in magnetoencephalography

We demonstrate noise characterization of novel 894.4 nm vertical-cavity surface emitting lasers with intracavity contacts and a rhomboidal oxide current aperture (IC-VCSELs), dedicated to 133Cs D1 line compact optically pumped atomic magnetometers (OPM). The laser relative intensity noise, measured to be -139 dB/Hz at 10 kHz frequency in 1 Hz bandwidth for a laser optical power of 0.8 mW, is decreased with optical power growth. The IC-VCSELs polarization-resolved relative intensity noise is 143 dB/Hz at 10 kHz frequency in 1 Hz bandwidth for 0.8 mW. The emission linewidth of the VCSEL is about 55 MHz. The IC-VCSEL parameters are determined, such as emission linewidth ~ 50-60 MHz, optical power ~ 0.5-1.0 mW, at which the polarization-resolved RIN becomes close to the RIN, which makes it possible to use these lasers in various OPM Mz and Mx schemes. The ultimate sensitivity of OPM was estimated by the ratio of the magnetic resonance to the signal to noise level. It is shown that a OPM based on the IC-VCSELs, assuming magnetic resonance FWHM ~ 1 kHz, can achieve a shot noise-limited sensitivity around 20 fT in 1 Hz bandwidth without any polarization improvements by polarizer or polarization beam splitter cube (PBC). Developed IC-VCSELs is acceptable for use in compact OPM for magnetoencephalography.

Examination of New York City Transit’s Bus and Subway Ridership Trends During the COVID-19 Pandemic

The New York City metropolitan area was hard hit by COVID-19, and the pandemic brought with it unprecedented challenges for New York City Transit. This paper addresses the techniques used to estimate dramatically changing ridership, at a time when previously dependable sources suddenly became unavailable (e.g., local bus payment data, manual field checks). The paper describes alterations to ridership models, as well as the expanding use of automated passenger counters, including validation of new technology and scaling to account for partial data availability. The paper then examines the trends in subway and bus ridership. Peak periods shifted by both time of day and relative intensity compared with the rest of the day, but not in the same way on weekdays and weekends. On average, trip distances became longer for subway and local bus routes, but overall average bus trip distances decreased owing to a drop in express bus usage. Subway ridership changes were compared with neighborhood demographic statistics and numerous correlations were identified, including with employment, income, and race and ethnicity. Other factors, such as the presence of hospitals, were not found to be significant.