Strain-induced control of a pillar cavity-GaAs single quantum dot photon source

Herein, we present the calculated strain-induced control of single GaAs/AlGaAs quantum dots (QDs) integrated into semiconductor micropillar cavities. We show precise energy control of individual single GaAs QD excitons under multi-modal stress fields of tailored micropillar optomechanical resonators. Further, using a three-dimensional envelope-function model, we evaluated the quantum mechanical correction in the QD band structures depending on their geometrical shape asymmetries and, more interestingly, on the practical degree of Al interdiffusion. Our theoretical calculations provide the practical quantum error margins, obtained by evaluating Al-interdiffused QDs that were engineered through a front-edge droplet epitaxy technique, for tuning engineered QD single-photon sources, facilitating a scalable on-chip integration of QD entangled photons.

Modal Stress Analysis of a Cracked Woven Composite Beam under Compression

In this study, modal stress analysis of carbon fiber plain weave cracked composite beams under compression is considered. General-purpose finite element code MSC. Marc is used for the finite element beam models. Before understanding the compression effect on the beam, dynamic characteristics of the models are compared with the experimental evaluations. Investigation of quasi-static and dynamic (equivalent von Mises stress and elastic strain energy density) behavior of the plain weave cracked beams with two different thicknesses under compression is examined numerically. Results are given in tabular and graphical form.

Utilization of modal stress approach in random-vibration fatigue evaluation

Random-vibration fatigue evaluation can be of considerable importance in the design phase of aerospace structures due to the severe dynamic loads in service. This paper presents the utilization of modal stress approach to the issue of structural random-vibration fatigue evaluation. Prognosis of random fatigue hotspots by using stress mode shapes is theoretically demonstrated. A two-step procedure is proposed for computational efficiency. Firstly, modal stress analysis is conducted to locate the fatigue hotspots in a dynamic structure. Secondly, the frequency domain-based approach for random fatigue evaluation is performed at these hotspots, as opposed to the computation of the entire structure as before. The capability of stress mode shapes to locate fatigue hotspots is verified by numerical investigations. The finite element model of a single-lap plate structure containing various opening holes was constructed for case study. Six elements were identified as hotspots by using modal stress distributions. Then, random responses and fatigue evaluation of the entire structure were carried out for verification. Good agreement was observed between the fatigue damage contour and the modal stress distributions, which can indicate that the critical positions predicted by stress mode shapes have good accuracy. The calculation time and storage space can be significantly reduced by means of the proposed evaluation procedure. Therefore, the accuracy and efficiency of utilization of modal stress approach in random fatigue evaluation can be ensured.

Evaluation of Stress in Vibrating Cylindrical Shells due to Acoustic Loading Based on Theory of Shells

Acoustically induced vibration (AIV) is recognized as a vibration of piping systems caused by the acoustic loading at the downstream of the pressure reducing devices. For decades several industrial practices which are derived from past experiences, have been applied for the design of piping system, however it is known that the practices includes uneven design margins. Due to the increase of the large capacity reducing devices, the demands of the development of reasonable screening and design method for AIV are increasing. A detailed assessment of fatigue life using finite element analysis has become popular and clarified the effect of acoustic load on several specific components; however, there are no clear way to explain the susceptibility against AIV depending on its diameter and thickness. Therefore the discussions based on engineering principles are required. In this paper, the vibration of cylindrical shells due to acoustic loading was discussed based on the theory of cylindrical shells. Results of several numerical studies based on the theoretical formulas were presented on the natural frequency and modal stress of vibrating shells on various geometries. Thus, the key factors to affect the vibrating shell stresses were clarified and some simplified formula to evaluate the vibrating shell stress was proposed.