The sensing application of triboelectric nanogenerators (TENGs) has received wide attention, and the output characteristics are mainly determined by the surface charge density (sigma); however, it is still a huge challenge to improve their performance through an effective strategy. Herein, we reported a multilayered structure coupling piezoelectric and triboelectric effects by integrating a polarized BaTiO3/PVDF nanocomposite film as a piezoelectric layer into the TENG structure. Additionally, the surface polarization of the triboelectric layer acts as a negative charge trap, further coupling and enhancing transferred charges. This nanogenerator improves the surface charge density and charge transfer efficiency under the synergistic effects of interfacial polarization and electric field coupling. Compared with the output voltage of a single TENG structure, an increase of 282.7% is observed, and a pressure sensitivity of 1.072 V kPa-1 can be achieved. The markedly enhanced output performance is quite stable and reliable in harsh mechanical environments due to the high flexibility of the films. This strategy exhibits promising potential for developing practical, flexible energy harvesting and sensor monitoring devices.
The effect of ultra-fine bubble (UFB) mixtures on the flow properties of micellar solutions passing through small slits was investigated. Steady-shear viscosity and dynamic viscoelasticity were measured because their rheological properties were evaluated. The resultant steady-shear viscosity (complex viscosity) and relaxation time were changed by mixed UFB. Pressure drops for ultrapure water (UPW), silicone oil, and mixed UFB water agreed with the predictions. On the other hand, worm-like micellar solutions showed higher pressure drops than those of UPW alone. Interestingly, pressure drops of micellar solutions mixed with UFB were lower than those of micellar solution alone. Furthermore, the experimental results arranged in dimensionless forms based on the hydraulic diameter showed the difference between with and without UFB in the range of slit-width >= 84 mu m. For discussing these experimental results, elastic properties and flow-induced birefringence were observed. Mean elastic stresses and first normal stress difference were measured by jet thrust method. Those of micellar solutions were higher than those of micellar solutions without UFB. The magnitude of Weissenberg number was greater than the order of 103. Thus, the strong elastic properties exhibited an increase in pressure drop. Additionally, flow-induced birefringence was changed by mixed UFB. Flow properties were altered due to the change in the orientation of the worm-like micelles (flow-induced structure).
We present a novel hybrid 800 nm laser with a wide tuning range, high optical power and ultra-narrow linewidth with ⪆kHz tuning speeds and a small footprint. Tunable, narrow linewidth hybrid lasers around 800nm serve as an attractive choice for e.g. OCT, LIDAR and atomic transition locking in e.g. atomic clocks. The laser has a microring resonator based optical cavity. The laser has a tuning range of 45 nm and a maximum output power of 5 dBm. The intrinsic linewidth of the laser is measured at 22 kHz.
Understanding the transport of light in photonic scattering media is crucial for many application areas, such as atmospheric and climate sciences, oceanography, biophysics, powder technology, printing, solid-state lighting, and satellite observations. Transport theory describes the propagation of waves in scattering media, notably in a widely-used realistic situation like a slab in three dimensions (3D). The basic differential equation used in transport theory is the radiative transfer equation, which is equivalent to Boltzmann’s equation used in the kinetic theory of gases and neutron transport. A popular method describe light propagation in multiple scattering media is the Monte Carlo simulation of light transport, a statistical method that converges to the exact solution of the radiative transfer equation. To obtain a high accuracy, however, this method comes with the cost of extremely long computation times and high computational power requirements. Alternatives to the Monte Carlo simulations are analytical approximations to the radiative transfer equation, such as the PN approximation. Analytical methods are still significantly faster than the Monte Carlo simulations, and in certain configurations, the results of these analytical approximations match the accuracy of simulations.In this thesis, we study the light transport through photonic scattering media, specifically the position dependent energy density, by using the transport theory and experimental observations. We specifically focus on samples that consist of anisotropically scattering and absorbing scatterers, as common approximations to the radiative transfer equation fail for these samples and one is thus interested in the possible description in these regimes. We perform experiments to measure the position-dependent energy density inside 3D and quasi-2D samples that are in these regimes. Our results provide a better understanding of such samples, and provide a guideline to the applicability of analytical models as an alternative to Monte Carlo simulations.
