Initiation and Propagation of Transverse Cracking in Composite Laminates

The matrix cracking transverse to loading direction is usually the one of most common observations of damages in composite laminates. The initiation and propagation of transverse cracks have been a longstanding issue in the last few decades. In this paper, a three-dimensional stress analysis method based on the state space approach is used to compute the stresses, including the inter-laminar stresses near transverse cracks in laminated composites. The stress field is then used to estimate the energy release rate, from which the initiation and propagation of transverse cracking are predicted. The proposed method is illustrated by numerical solutions and is validated by available experimental results. To the best knowledge of the authors, the predictions of crack behaviour for non-symmetrical laminates and laminates subject to in-plane shearing are presented for the first time in the literature

Can life survive Gamma-Ray Bursts in the high-redshift universe?

Nearby Gamma-Ray Bursts (GRBs) have been proposed as a possible cause of mass extinctions on Earth. Due to the higher event rate of GRBs at higher redshifts, it has been speculated that life as we know it may not survive above a certain redshift (e.g. $z>0.5$). We examine the duty cycle of lethal (life-threatening) GRBs in the solar neighborhood, in the Sloan Digital Sky Survey (SDSS) galaxies and GRB host galaxies, with the dependence of the long GRB rate on star formation and metallicity properly taken into account. We find that the number of lethal GRBs attacking Earth within the past 500 Myr ($\sim$ epoch of the Ordovician mass extinction) is $0.93$. The number of lethal GRBs hitting a certain planet increases with redshift, thanks to the increasing star formation rate and decreasing metallicity in high-$z$ galaxies. Taking 1 per 500 Myr as a conservative duty cycle for life to survive, as evidenced by our existence, we find that there are still a good fraction of SDSS galaxies beyond $z=0.5$ where the GRB rate at half-mass radius is lower than this value. We derive the fraction of such benign galaxies as a function of redshift through Monte Carlo simulations, and find that the fraction is $\sim 50\%$ at $z\sim 1.5$ and $\sim 10\%$ even at $z \sim 3$. The mass distribution of benign galaxies is dominated by Milky-Way-like ones, thanks to their commonness, relatively large mass, and low star formation rate. GRB host galaxies are among the most dangerous ones.Comment: Accepted for publication in The Astrophysical Journal, 7 pages, 4 figures, 1 tabl

How Do Organizations Assess for Potential, in addition to a Talent Review Process?

Demand for high potential talent has increased dramatically in the past five years as companies have struggled to fill vacancies due to a competitive talent market. Therefore, having a strong talent pipeline is extremely critical to organizations. Most companies evaluate high potential talent based on three criteria: engagement, ability, aspiration to hold successive leadership. But only 53% of organizations are confident in their ability to select and assess the best talent. An efficient tool is necessary to assess and capture the best talent in the organization. These four categories of tools are widely used by industries and have been considered successful and effective when measuring potential leaders: Assessment and development centers External assessment tools Company self-developed assessment methods 360-degree employee feedback assessment To better understand the benefits of using these tools, this summary report will analyze the essence of the tools and provide case studies of top performers in the industry using these methods