Study of Balance Equations for Hot-Electron Transport in an Arbitrary Energy Band (III)

By choosing an electron gas resting instead of drifting in the laboratory coordinate system as the initial state, the first order perturbation calculation of the previous paper (Phys. Stat. Sol. (b) 198, 785(1996)) is revised and extended to include the high order field corrections in the expression for the frictional forces and the energy transfer rates. The final expressions are formally the same as those in first order in the electric field, but the distribution functions of electrons appearing in them are defined by different expressions. The problems relative to the distribution function are discussed in detail and a new closed expression for the distribution function is obtained. The nonlinear impurity-limited resistance of a strong degenerate electron gas is computed numerically. The result calculated by using the new expression for the distribution function is quite different from that using the displaced Fermi function when the electric field is sufficiently high.Comment: 15 pages with 3 PS figures, RevTeX, to be published in Physica Status Solidi (b

Development of electrochemical CO2 reduction to gas and liquid fuels in aqueous media with scale-up potential

Ph. D. ThesisElectrochemical CO2 reduction reaction (eCO2RR) in CO2 utilization field attracts large interests as it only consumes water and electricity as the inputs to build valuable carbonaceous fuels and chemicals (i.e., CO, formate, low-carbon oxygen-contained and oxygen-free hydrocarbons). However, in aqueous media, hydrogen evolution reaction (HER) competes with eCO2RR and theoretically much easier to be carried out resulting in low Faradaic efficiency (FE) towards eCO2RR. Aiming at developing eCO2RR system with supressed HER, this study enhanced CO2 mass transfer and reaction kinetics through cell configuration and electrolyte engineering, and developed the FE of valuable carbonaceous products by catalysts design. eCO2RR has been generally carried out by a two-chamber (2C) cell using CO2-saturated electrolyte, mass transfer is challenged by the CO2 solubility. This study constructed a gas diffusion electrode (GDE) cell that CO2 could be directly supplied to reaction interface with less resistance from the electrolyte, which greatly enhanced the overall FE for carbonaceous products compared with the 2C cell. The use of high alkalinity catholytes in GDE cell improved reaction kinetics and further increased FE of carbonaceous products, especially for C2 (ethanol and ethylene). C2 FE achieved 40% and current density reached -234 mA cm-2 at -1.17 V (RHE) with using 2.0 M KOH. Targeting to enhance the selectivity of CO, a simple synthesis procedure for Cu-In catalyst was developed by electrochemical spontaneous precipitation (ESP) method. The material possessed a hybrid structure of amorphous In(OH)3 nano-layer capping on polycrystalline CuxO, which structurally facilitated Cu-In interaction. CO production using Cu-In catalyst reached ~90% FE and -200 mA cm-2 current density at -1.17 V (RHE). Syngas with tunable CO/H2 ratio could be also produced by changing the ESP condition. Carbon supported SnO2 catalyst was studied for selective formate production (>80% FE). High concentration (0.5 M) of formate solution was produced within 1-hour CO2 reduction, which was utilized for a direct formate fuel cell (DFFC). The DFFC used Pd-CeO2/C anode and FeCo/C cathode, producing 92 mW cm-2 peak power density at 30% energy efficiency. A close loop of “electricity-formate-electricity” was realized, illustrating the important potential of synthetic liquid fuels from CO2 for energy storage and transportation applications.EPSRC LifesCO2R projec

Analysis and optimization of temperature distribution in carbon fiber reinforced composite materials during microwave curing process

Vacuum assisted microwave curing technologies and modified optical sensing systems have been employed to investigate the influence of ply orientation and thickness on through-thickness temperature distribution of carbon fiber reinforced composite laminates. Two different types of epoxy systems have been studied. The results demonstrated that the ply orientation did not affect the temperature distribution of composite materials. However, the thickness was an important influencing factor. Nearly 10 ◦C temperature difference was found in 22.5 mm thick laminates. Through analyzing the physical mechanisms during microwave curing, the temperature difference decreased when the heat-loss in surface laminates was reduced and the absorption of microwave energy in the center laminates was improved. The maximum temperature difference of the samples formed using the modified microwave curing technologies in this research could be reduced by 79% to 2.1 ◦C. Compared with the 5.29 ◦C temperature difference of laminates using thermal heating process, the maximum temperature difference in laminates using modified microwave curing technologies was reduced by 60%, and the curing time was cut down by 25%

Sharp bounds for a class of integral operators in weighted-type spaces on Heisenberg group

In this paper, we will use the conclusions and methods in \cite{1} to obtain the sharp bounds for a class of integral operators with the nonnegative kernels in weighted-type spaces on Heisenberg group. As promotions, the sharp bounds of Hardy operator , Hardy Littlewood-P\'{o}lya operator and Hilbert operator are also obtained

Gauge dependence of spontaneous radiation spectrum of relativistic atomic beam under non-uniform electrostatic field

Gauge theory requires physical observables to be gauge-independent. However, ever since Lamb noticed the problem of gauge selection in calculating atomic spontaneous radiation spectrum, the problem of gauge dependence was encountered in many fields of physics research. Therefore, it is important to test the self-consistency of gauge symmetry for various physical systems. In this paper, we calculate the transient spontaneous radiation spectrum of a relativistic hydrogen atom in the non-uniform electrostatic field under the atomic self-reference frame. The physical system studied in this paper is a frame-transformed version of our recent work [\href{https://link.springer.com/paper/10.1140/epjd/s10053-022-00407-5}{Euro. J. Phys. D \textbf{76}, 84(2022)}] where the radiating object is static while the charge is moving relativistically. The obtained peak frequency can differ by about $413$ $\mathrm{KHz}$ or larger for the commonly used Coulomb, Lorentz, and multipolar gauges. This observation can be significant not only for studying how the gauge field interacts with the quantum system in theory, but also for practical experimental applications, such as the timing accuracy of atomic clocks in the external electromagnetic field