Thrust performance of a variable-geometry, divergent exhaust nozzle on a turbojet engine at altitude

A variable geometry, low aspect ratio, nonaxisymmetric, two dimensional, convergent-divergent exhaust nozzle was tested at simulated altitude on a turbojet engine to obtain baseline axial, dry thrust performance over wide ranges of operating nozzle pressure ratios, throat areas, and internal expansion area ratios. The thrust data showed good agreement with theory and scale model test results after the data were corrected for seal leakage and coolant losses. Wall static pressure profile data were also obtained and compared with one dimensional theory and scale model data. The pressure data indicate greater three dimensional flow effects in the full scale tests than with models. The leakage and coolant penalties were substantial, and the method to determine them is included

Origination, diversity, and extinction metrics essential for analysis of mass biotic crisis events: An example from cretaceous ammonoidea

Traditional mass extinction research has predominently concentrated on statistically demonstrating that mass extinction intervals are significantly above background levels of familial and generic extinction in terms of extinction percentage, extinction rate, and per-taxon extinction rate; mass extinction intervals occur on a set periodicity throughout geologic time, which is estimated to be some 30 MYR in duration. The published literature has given little emphasis to equally important considerations and metrics such as origination rate, standing diversity, and rate of generation of new taxa DURING mass extinction intervals. The extent to which a mass extinction affects the regional or global biota, must ultimately be gauged by taking into consideration both the number of taxa which become extinct at or near the event (stage) boundary, and the number of taxa which are either not affected at all by the extinction or actually evolved during or shortly before/after the extinction interval. These effects can be seen in Cretaceous Ammonoidea (at the genus level), and their combined usage allow better insight into paleobiological dynamics and responses to mass extinction and its affect on this dominant Molluscan organism

What Influences the Diffusion of Grassroots Innovations for Sustainability? Investigating Community Currency Niches

Community action for sustainability is a promising site of socio-technical innovation. Here we test the applicability of co-evolutionary niche theories of innovation diffusion (Strategic Niche Management, SNM) to the context of ‘grassroots innovations’. We present new empirical findings from an international study of 12 community currency niches (such as LETS, time banks, local currencies). These are parallel systems of exchange, designed to operate alongside mainstream money, meeting additional sustainability needs. Our findings confirm SNM predictions that niche-level activity correlates with diffusion success, but we highlight additional or confounding factors, and how niche theories might be adapted to better fit civil-society innovations. In so doing, we develop a model of grassroots innovation niche diffusion which builds on existing work and tailors it to this specific context. The paper concludes with a series of theoretically-informed recommendations for practitioners and policymakers to support the development and potential of grassroots innovations

Applying Genetic Programming to Bytecode and Assembly

Traditional genetic programming (GP) is typically not used to perform unrestricted evolution on entire programs at the source code level. Instead, only small sections within programs are usually evolved. Not being able to evolve whole programs is an issue since it limits the flexibility of what can be evolved. Evolving programs in either bytecode or assembly language is a method that has been used to perform unrestricted evolution. This paper provides an overview of applying genetic programming to Java bytecode and x86 assembly. Two examples of how this method has been implemented will be explored. We will also discuss experimental results that include evolving recursive functions and automated bug repair

A Quasi-Experimental Investigation of Tennessee Promise and Career and Technical Education Postsecondary Enrollment Responses

In this study I deployed quasi-experimental methods to explore the effect of the implementation of a statewide free-college program, Tennessee Promise, on enrollment in postsecondary career and technical education programs. State policymakers implemented the Tennessee Promise, a free-college program for recent high school graduates attending public, two-year institutions, in 2015. As postsecondary attainment in the United States falls short of workforce needs, there has been an increased focus on postsecondary career and technical education credentials and degrees linking workforce needs directly with educational programs (Lumina, 2019; Perkins V, 2019). However, it is currently unknown whether access to statewide free-college funding impacts enrollment in postsecondary career and technical education. In this study, I use federal data to estimate the causal effect of Tennessee Promise on postsecondary career and technical education enrollment. Findings from the analysis show a small but non-significant increase in Tennessee after the implementation of the grant when compared to both the national control group and the contiguous control group. I discuss the implications for research and practice, and how promise programs may be leveraged more effectively moving forward to improve outcomes in postsecondary career and technical education