Progressive failure analysis of fibrous composite materials and structures

A brief description is given of the modifications implemented in the PAFAC finite element program for the simulation of progressive failure in fibrous composite materials and structures. Details of the memory allocation, input data, and the new subroutines are given. Also, built-in failure criteria for homogeneous and fibrous composite materials are described

Auger Spectra and Different Ionic Charges Following 3s, 3p and 3d Sub-Shells Photoionization of Kr Atoms

The decay of inner-shell vacancy in an atom through radiative and non-radiative transitions leads to final charged ions. The de-excitation decay of 3s, 3p and 3d vacancies in Kr atoms are calculated using Monte-Carlo simulation method. The vacancy cascade pathway resulted from the de-excitation decay of deep core hole in 3s subshell in Kr atoms is discussed. The generation of spectator vacancies during the vacancy cascade development gives rise to Auger satellite spectra. The last transitions of the de-excitation decay of 3s, 3p and 3d holes lead to specific charged ions. Dirac-Fock-Slater wave functions are adapted to calculate radiative and non-radiative transition probabilities. The intensity of Kr^{4+} ions are high for 3s hole state, whereas Kr^{3+} and Kr^{2+} ions have highest intensities for 3p and 3d hole states, respectively. The present results of ion charge state distributions agree well with the experimental data.Comment: Published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA

The State of Digital Investments in MENA 2013–2016

Digital entrepreneurship and innovation remain focal points for government leaders across the MENA region as they develop their economic strategies. This investment report aims to help investors and policymakers to measure and identify the strengths and gaps in their ecosystems, while monitoring the impact of their policies and programs. The report covers more than 150 funding institutions and 760 transactions that took place between 2013 and 2016. The MENA region witnessed a record year in technology start-up funding in 2016 with more than 30 new investment institutions launched and more than $900 million invested, equaling more than the value of all investments between 2013 and 2015 combined (approximately$750 million). The report analyzes year-on-year digital investment trends in the MENA such as information on investors, investments, inactive versus active start-ups, number of female founders in funded start-ups and corporate investors. This is an annual report, which endeavors on updating both its historical and current data thus ensuring that the analysis is more robust and the findings are more comprehensive. The report utilized three data collection methods. First, findings are based on data collected from 75 investors and accelerators in the MENA region. Second, the report aggregated information from publicly available data. Third, the report collected new data from start-ups through surveys. All investments analyzed in the report are for equity-based investments only, and therefore institutions that provide grant or non-equity funding have not been included in the analysis. Hence, the paper will tackle three main themes related to technology investments in the MENA region. These four themes include: (1) investors in MENA, (2) investors in MENA by ticket size, (3) investments in MENA, and (4) valley of death.     Keywords: digital, technology, investors, investments, start-up

Prediction of the flow inside a micro gas turbine combustor

The main purpose of this study is to predict the flow dynamics inside a micro gas turbine combustor model. The flow field inside the combustor is controlled by the liner shape and size, wall side holes shape, size and arrangement (primary, secondary and dilution holes), and primary air swirler configuration. Air swirler adds sufficient swirling to the inlet flow to generate central recirculation region (CRZ) which is necessary for flame stability and fuel air mixing enhancement. Therefore designing an appropriate air swirler is a challenge to produce stable, efficient and low emission combustion with low pressure losses. Four axial flat vane swirlers with 20 °, 30 °, 45 ° and 60 ° vane angle corresponding to swirl number of 0.27, 0.42, 0.74, and 1.285 respectively were used in this analysis to show vane angle effect on the internal flow field. The flow behavior was investigated numerically using CFD solver FLUENT 6.2. This study has provided physical insight into the flow pattern inside the combustion chamber. Results show that the swirling action is augmented with the increase in the vane angle, which leads to increase in the turbulence strength, recirculation zone size, and amount of recirculated mass. However, all these happen at the expense of the increase in pressure losses. In case of 20 ° swirler (swirl number < 0.4), the produced swirling flow is not enough to generate CRZ