New Irregular Mesh Technique Used in Three-Dimensional Simulation of Relaxation Semiconductors

The aim of this work is to simulate correctly in 3D space the phenomena that govern relaxation semiconductors. To avoid the relevant constraints of inadequate mesh a new technique for refining irregular meshing has been creating. Each length of the sample will be considered as a partial sum of a geometric series, the calculation of the argument of this series, will allow to calculate the distance between the nodes. In this paper we proposed to use an algorithm combined between Gummel and Newton Raphson algorithms to solve the partial differential equations, the linearization of transport equations is obtained by applying the finite difference method, which allowed us to calculate the relaxation time, life time and recombination rate. The results revealed appearance of a limited region called recombination front instead of charge space region, an improvement in computational time with a big precision for a 3D simulation, by letting to the user the choice of the distance to be discreet and the number of points wished without saturate the memory. This type of meshing is simple to apply and can be used to be applied as a solution to correctly simulate phenomena in structures at different areas for all the dimensions.

A STUDY OF THE COMBUSTION OF HIGH-DENSITY PROPELLANTS IN A MODEL BALLISTIC INSTALLATION

In internal ballistics of barrel systems, a promising trend is related to the increasing of projectile muzzle velocity by means of high-energy propellants utilized as a traveling charge. The use of a loading scheme with a traveling charge allows one to increase the loading density and to redistribute the energy of powder gases in the space behind the projectile, which leads to a significant increase in the muzzle velocity of the projectile. To attain the listed advantages, it is necessary to know the laws of dispersion and combustion of the propellants used as traveling charges, providing non-digressive gas entry into the charge space. In this work, a comprehensive experimental and theoretical study of the laws of dispersion and combustion of high-density propellants under dynamic pressures, provided in a model ballistic installation, is carried out. The main ballistic characteristics of shots are obtained, which use a classic scheme of loading with a propellant charge made of pyroxylin powder and a scheme with a traveling charge, where, in addition to the propellant charge, a high-density propellant is included. All the experiments are simulated in a software package, taking into account the presence of the high-density propellants in the propellant charge, dispersing into individual particles that burn out while moving along the barrel. As a result of comparing the calculated and experimental data, plausible patterns of the distribution of gas-dynamic parameters are obtained using the classic loading scheme and the loading scheme with a travelling high-density propellant charge.

DIGITAL CONTACT POTENTIAL PROBE IN STUDYING THE DEFORMATION OF DIELECTRIC MATERIALS

The paper reviews the results of a study on the surface electrostatic charges of dielectrics obtained using the contact potential difference (CPD) technique. Initially, the CPD technique was only applied to the study of metal and semiconductor surfaces. The conventional CPD measurement technique requires full compensation of the measured potential that, in the case of dielectrics, could reach very high values. Such high potentials are hard to compensate. Therefore, the conventional CPD method is rarely applied in the study of dielectric materials. Some important improvements recently made to the CPD measurement technique removed the need for compensation. The new method, which does not require compensation, has been implemented in the form of a digital Kelvin probe. The paper describes the principles of the non-compensation CPD measurement technique which was developed for mapping the electrostatic surface charge space distribution across a wide range of potential values. The study was performed on polymers such as low-density polyethylene (LDPE) and polytetrafluoroethylene (PTFE).

Author Correction: Boosting output performance of sliding mode triboelectric nanogenerator by charge space-accumulation effect

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Boosting output performance of sliding mode triboelectric nanogenerator by charge space-accumulation effect

The sliding mode triboelectric nanogenerator (S-TENG) is an effective technology for in-plane low-frequency mechanical energy harvesting. However, as surface modification of tribo-materials and charge excitation strategies are not well applicable for this mode, output performance promotion of S-TENG has no breakthrough recently. Herein, we propose a new strategy by designing shielding layer and alternative blank-tribo-area enabled charge space-accumulation (CSA) for enormously improving the charge density of S-TENG. It is found that the shielding layer prevents the air breakdown on the interface of tribo-layers effectively and the blank-tribo-area with charge dissipation on its surface of tribo-material promotes charge accumulation. The charge space-accumulation mechanism is analyzed theoretically and verified by experiments. The charge density of CSA-S-TENG achieves a 2.3 fold enhancement (1.63 mC m−2) of normal S-TENG in ambient conditions. This work provides a deep understanding of the working mechanism of S-TENG and an effective strategy for promoting its output performance.

Precharging Photon Upconversion: Interfacial Interactions in Solution-Processed Perovskite Upconversion Devices

<p>Recent advances in perovskite-sensitized photon upconversion via triplet-triplet annihilation (TTA) in rubrene have yielded several unanswered questions about the underlying mechanism and processes occurring at the interface. In particular, the near-infrared perovskite emission is not significantly quenched and a rapid reversible photobleach of the upconverted emission can be observed under fairly low excitation densities of 3.2 mW/cm2. In this contribution, we investigate the perovskite/organic interface in more detail and conclude that non-covalent interactions between the organic layer and perovskite result in surface trap passivation. In addition, band bending results in a charge space region at the perovskite/rubrene interface, which precharges the rubrene interface with holes. Upon initial illumination, electrons can rapidly transfer to the excited triplet state of rubrene, followed by efficient TTA upconversion. As the device is continuously illuminated, the precharged holes are consumed and a new equilibrium is reached, resulting in the previously investigated steady-state upconversion efficiency.</p>

Precharging Photon Upconversion: Interfacial Interactions in Solution-Processed Perovskite Upconversion Devices

<p>Recent advances in perovskite-sensitized photon upconversion via triplet-triplet annihilation (TTA) in rubrene have yielded several unanswered questions about the underlying mechanism and processes occurring at the interface. In particular, the near-infrared perovskite emission is not significantly quenched and a rapid reversible photobleach of the upconverted emission can be observed under fairly low excitation densities of 3.2 mW/cm2. In this contribution, we investigate the perovskite/organic interface in more detail and conclude that non-covalent interactions between the organic layer and perovskite result in surface trap passivation. In addition, band bending results in a charge space region at the perovskite/rubrene interface, which precharges the rubrene interface with holes. Upon initial illumination, electrons can rapidly transfer to the excited triplet state of rubrene, followed by efficient TTA upconversion. As the device is continuously illuminated, the precharged holes are consumed and a new equilibrium is reached, resulting in the previously investigated steady-state upconversion efficiency.</p>