ESSE 2017. Proceedings of the International Conference on Environmental Science and Sustainable Energy

Environmental science is an interdisciplinary academic field that integrates physical-, biological-, and information sciences to study and solve environmental problems. ESSE - The International Conference on Environmental Science and Sustainable Energy provides a platform for experts, professionals, and researchers to share updated information and stimulate the communication with each other. In 2017 it was held in Suzhou, China June 23-25, 2017

Optically active quantum dots in bottom-up nanowires

This thesis is dedicated to the discovery and progressive study of quantum emitters embedded in the shell of coaxial gallium arsenide/ aluminum gallium arsenide nanowires. The bottom-up core/shell nanowires were grown in a molecular beam epitaxy machine. During the shell growth, diffusion-driven phenomena lead to segregation effects. Gallium-rich regions are formed at the nanoscopic scale. The observation has been made that the reduced dimensionality of these regions provides true tridimensional confinement for the carriers. The recombination spectra of the electrons with the holes in what was coined shell quantum dots (shell-QDs) thus appear as sets of narrow, intense peaks. The formation of shell quantum dots is taking place on a large range of growth temperatures and nominal alloy fractions, giving freedom to engineer the growth process. The shell thickness plays an important role in the quantum dot density and total ensemble spectrum. In addition, the adjunction of an aluminum arsenide predeposition layer increasing the local curvature has been seen to foster the quantum dots formation. Single emitter spectroscopy reveals the few-particles electronic structure of quantum dots, with systematic signatures for the different degrees of occupation of the quantum dot. The shape anisotropy of the quantum dots leads to observable spin-spin interactions, which lift the degeneracy of the exciton level (one hole and one electron). Generally undesirable, this effect allows here to find that the orientation of the quantum dots in the nanowire is not hard-wired to the growth direction or to the nanowire long axis. This observation is confirmed by magneto-photoluminescence experiments. The energetic splitting and shift of the spin sublevels when an external magnetic field is applied also confirms the small size of the quantum dots. It is found that for GaAs in the strong confinement regime, the Landé coefficients of the electron and hole take opposite signs and are dependent on the angle at which the field is applied. These effects allow to tune the exciton composite Landé coefficient and could be used to reduce the splitting between the exciton spin sublevels or create optically degenerate coupled systems. Finally, the sub-nanosecond dynamics happening in the quantum dots are probed with time-correlated photon counting. It is shown that the carriers in the shell are quickly captured by the quantum dots. In addition, it is proposed that the electron population is reduced due to diffusion-assisted mechanisms or through electron-donor recombination

Spacelab Science Results Study

Beginning with OSTA-1 in November 1981 and ending with Neurolab in March 1998, a total of 36 Shuttle missions carried various Spacelab components such as the Spacelab module, pallet, instrument pointing system, or mission peculiar experiment support structure. The experiments carried out during these flights included astrophysics, solar physics, plasma physics, atmospheric science, Earth observations, and a wide range of microgravity experiments in life sciences, biotechnology, materials science, and fluid physics which includes combustion and critical point phenomena. In all, some 764 experiments were conducted by investigators from the U.S., Europe, and Japan. The purpose of this Spacelab Science Results Study is to document the contributions made in each of the major research areas by giving a brief synopsis of the more significant experiments and an extensive list of the publications that were produced. We have also endeavored to show how these results impacted the existing body of knowledge, where they have spawned new fields, and if appropriate, where the knowledge they produced has been applied

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen