A New Discrete Implicit Monte Carlo Scheme for Simulating Radiative Transfer Problems

We present a new algorithm for radiative transfer—based on a statistical Monte Carlo approach—that does not suffer from teleportation effects, on the one hand, and yields smooth results, on the other hand. Implicit Monte Carlo (IMC) techniques for modeling radiative transfer have existed from the 1970s. When they are used for optically thick problems, however, the basic algorithm suffers from “teleportation” errors, where the photons propagate faster than the exact physical behavior, due to the absorption-blackbody emission processes. One possible solution is to use semianalog Monte Carlo, in its new implicit form (ISMC), which uses two kinds of particles, photons and discrete material particles. This algorithm yields excellent teleportation-free results, but it also produces noisier solutions (relative to classic IMC), due to its discrete nature. Here, we derive a new Monte Carlo algorithm, Discrete Implicit Monte Carlo (DIMC), which also uses the idea of two kinds of discrete particles, and thus does not suffer from teleportation errors. DIMC implements the IMC discretization and creates new radiation photons for each time step, unlike ISMC. Using the continuous absorption technique, DIMC yields smooth results like classic IMC. One of the main elements of the algorithm is the avoidance of the explosion of the particle population, by using particle merging. We test the new algorithm on 1D and 2D cylindrical problems, and show that it yields smooth, teleportation-free results. We finish by demonstrating the power of the new algorithm on a classic radiative hydrodynamic problem—an opaque radiative shock wave. This demonstrates the power of the new algorithm for astrophysical scenarios.

Cloud Phase Recognition Based on Oxygen A Band and CO2 1.6 µm Band

The accurate recognition of the cloud phase has a great influence on the retrieval of the cloud top height. In order to improve the accuracy of obtaining the cloud top height with OCO-2, we proposed a cloud phase recognition algorithm based on the threshold of parameter α; α is defined as the reflectivity ratio of the region with weak continuous absorption of the oxygen A band to the region with weak continuous absorption of the CO2 1.6 µm band. The α under different solar zenith angles and different ground albedos was calculated. The results show the following: under the same surface albedo and solar zenith angle, α was large for ice clouds and small for water clouds. Under the same surface albedo, the greater the solar zenith angle, the smaller the α of the ice cloud, and the larger the α of the water cloud. Under the same solar zenith angle, the greater the surface albedo, the smaller the α; when the solar zenith angle was less than 70°, α can be used to effectively distinguish between the ice cloud and water cloud. This study used OCO-2 data of a single orbit over ocean to verify the feasibility of the algorithm through comparison with the CALIOP cloud phase product, which provided a basis for OCO-2 cloud top height estimation.

Semiconductor Quantum Dots

Semiconductor particles in the range of 2-10 nm are known as quantum dots (QDs) and nano-crystals where in all the three spatial dimensions, excitons are confined. Because of very small size and special electronic properties, QDs are expected to be building blocks of many electronic and optoelectronic devices. These particles possess tunable quantum efficiency, continuous absorption spectra, narrow emission and long term photostability. These are important for various biomedical applications. In this chapter definition of semiconductor QDs, their methods of preparation and characterization along with their properties and applications have been discussed.

Development of a Panel Membrane Resonant Absorber

The bass ratio describes the relationship between the reverberation energy in the low frequency region and that of the middle frequency. An appropriate bass ratio can create a warm sound; however, too much bass can influence speech clarity (C50) and work efficiency and can even cause listeners to feel tired or exhausted. Using perforated plate resonance theory and membrane resonance theory, this research developed the panel membrane resonant absorber (PMRA), which not only provides an outstanding continuous absorption spectrum in the broadband range of 100–800 Hz but also presents an aesthetic appearance at a low cost. We divided this study into two parts: (1) PMRA development and experiment and (2) field application and measurement to confirm the sound absorption performance of the PMRA. In part 1, PMRA was developed by combining different materials and thicknesses of the air cavity. In the field study of part 2, the PMRA with the appropriate sound-absorbing curve was installed in a small auditorium, where we conducted field measurements for reverberation time (RT) and speech clarity (C50). According to the experimental results, the PMRA had great absorption performance at a low frequency. In the field validation, the PMRA was found to effectively decrease the low-frequency RT while also maintaining the RT of middle-high frequency. The C50 of the auditorium was also improved.

Quantum electromechanics with levitated nanoparticles

Preparing and observing quantum states of nanoscale particles is a challenging task with great relevance for quantum technologies and tests of fundamental physics. In contrast to atomic systems with discrete transitions, nanoparticles exhibit a practically continuous absorption spectrum and thus their quantum dynamics cannot be easily manipulated. Here, we demonstrate that charged nanoscale dielectrics can be artificially endowed with a discrete level structure by coherently interfacing their rotational and translational motion with a superconducting qubit. We propose a pulsed scheme for the generation and read-out of motional quantum superpositions and entanglement between several levitated nanoparticles, providing an all-electric platform for networked hybrid quantum devices.

Function of Interface Deposition of Calcium Sulfate in Pressure Acid Leaching of Black Shale-Hosted Vanadium

During pressure acid leaching process of black shale-hosted vanadium, increasing the reaction interface of muscovite dissolution can enhance the vanadium release. In this paper, calcium sulfate (CaSO4) deposition behavior and its effect on muscovite under K2SO4 assistance were focused on for demonstrating the function of CaSO4 on vanadium leaching from the black shale. Results showed that as K2SO4 mediated, the apparent activation energy of vanadium leaching and the apparent reaction order of sulfuric acid decreased from 24.37 kJ/mol to 16.63 kJ/mol and 2.7 to 1.9, respectively. The leaching rate and dependence on pH value were modified. The vanadium leaching acceleration owed to CaSO4 deposition on muscovite in the black shale. The ion absorption stimulations found that Ca2+ is confirmed to be easily absorbed on the six-membered ring cavity of silicon-oxygen tetrahedrons in muscovite structure prior to K+ and Na+. Meanwhile, SO42− provides two oxygen atoms to bond with Ca2+ absorbed on muscovite (001) surface. The continuous absorption and bonding create CaSO4 deposition on muscovite (001) surface which also involves the load transmitting. The stress load transmitting correlates to pore formation in muscovite particles. It was proved that massive micropores initiated and proliferated in the existing pores under K2SO4 assistance. The porosity caused by CaSO4 deposition greatly increased the reaction interface of muscovite dissolution and accelerate internal diffusion of H+ to the reaction interface, which can significantly weaken the vanadium leaching dependence on acid.