A study to improve the mechanical properties of silicon carbide ribbon fibers

Preliminary deposition studies of SiC ribbon on a carbon ribbon substrate showed that the dominant strength limiting flaws were at the substrate surface. Procedures for making the carbon ribbon substrate from polyimide film were improved, providing lengths up to 450 meters (1,500 ft.) of flat carbon ribbon substrate 1,900 microns (75 mils) wide by 25 microns (1 mil) thick. The flaws on the carbon ribbon were smaller and less frequent than on carbon ribbon used earlier. SiC ribbon made using the improved substrate, including a layer of pyrolytic graphite to reduce further the severity of substrate surface flaws, showed strength levels up to the 2,068 MPa (300 Ksi) target of the program, with average strength levels over 1,700 MPa (250 Ksi) with coefficient of variation as low as 10% for some runs

What Should EDA Fund? Developing a Model for Pre-Assessment of Economic Development Investments

This paper describes the completion of a “comprehensive study of regionalism” that was conducted by a joint team of economists and economic development specialists for the Economic Development Administration (EDA). The project consisted of two main activities: an examination of the factors associated with economic development success and the creation of a practical interactive tool for EDA project assessment and comparison. Findings from surveys, interviews, and project case studies are discussed in terms of their support for a positive relationship between successful economic development efforts and factors such as leadership and private investment. Also, the authors discuss the creation of a quantitative assessment model utilizing well-known approaches such as economic impact multipliers and cluster theory. The primary contribution of this work to the existing body of EDA-focused research and evaluation literature is introducing a means of using standardized scores, also known as z-scores, to compare and assess economic development projects across both industries and regions.regional economic development, economic impact, assessment model, EDA, z-score

3. Launching the New Enterprise

As the academic year of 1945-46 approached, the intensity of activity in preparation for actually opening the school in the fall term became overwhelming. Incredible though it may seem, Ives and Day were able in a period of a few weeks to assemble the nucleus of a faculty, several of whom formed a continuing source of counsel and advice both during the school’s formative years and thereafter. Includes: The First Dean and the School’s Dedication; A Participant’s View of the Early Years; Ives Moves On; Several Views of Martin P. Catherwood; The Founders

Exploring Supervision Fees in Four Probation Jurisdictions in Texas

In 2014, the University of Minnesota's Robina Institute of Criminal Law and Criminal Justice began a multi-state study that was tasked with exploring nationwide variations in the practices and policies of probation violations and revocations. A distinctive finding that grew out of the Robina Institute's work in two Texas counties was that probation supervision fees play a major role throughout the state. Probationers are required as one of 25 standard conditions to pay supervision fees, and—depending on the case— they may have to pay additional program fees, fines, and restitution. Texas probation departments depend on supervision fees for a large share of their operating budgets, and they are responsible for collecting those fees. Because payment of fees is a formal condition of probation, probationers may be sanctioned if they fall delinquent. Additionally, their probation terms may be extended to allow more time to pay, or early termination may be denied. In interviews, some probationers believed they could be revoked to jail or prison for failure to pay supervision fees. However, we heard from probation officers that probationers were not revoked solely for fees. The officers told us that nonpayment may be one reason probationers are revoked, but only when combined with other violations.The Robina Institute was encouraged by other probation chiefs in Texas to add additional counties to our study. To understand the interaction between probation and criminal justice fees in greater depth, the Robina Institute conducted a mixed methods study with 4 probation jurisdictions in Texas. Quantitative data was analyzed to examine the average amount of fees ordered, the breakdown of the fees ordered, and the percent of probationers who were current and delinquent on their fees. The quantitative analysis also examined the outcomes for those who were delinquent on their fees. Qualitative interviews were conducted with probationers to understand how fees impacted them and their experience of probation, as well as how they handled paying their fees. Probation officers were also interviewed to examine how fees were utilized and how officers collected fees.This report highlights some of the findings from qualitative interviews with over 50 probation officers and 46 probationers in 4 probation jurisdictions. A separate report highlights our quantitative findings; future Robina Institute publications will explore the quantitative and qualitative data in greater depth, as well as legal issues associated with the imposition and collection of supervision fees.The first section of this report presents findings from the focus groups with the probation officers. The second section focuses on findings from the probationer focus groups

Exercise-Induced Changes in the Cortical Bone of Growing Mice Are Bone and Gender Specific

Fracture risk and mechanical competence of bone are functions of bone mass and tissue quality, which in turn are dependent on the bone's mechanical environment. Male mice have a greater response to non-weight-bearing exercise than females, resulting in larger, stronger bones compared with control animals. The aim of this study was to test the hypothesis that short-term weight-bearing running during growth (21 days starting at 8 weeks of age; 30 min/day; 12 m/min; 5° incline; 7 days/week) would similarly have a greater impact on cross-sectional geometry and mechanical competence in the femora and tibiae of male mice versus females. Based on the orientation of the legs during running and the proximity of the tibia to the point of impact, this response was hypothesized to be greatest in the tibia. Exercise-related changes relative to controls were assayed by four-point bending tests, while volumetric bone mineral density and cross-sectional geometry were also assessed. The response to running was bone- and gender-specific, with male tibiae demonstrating the greatest effects. In male tibiae, periosteal perimeter, endocortical perimeter, cortical area, medial–lateral width and bending moment of inertia increased versus control mice suggesting that while growth is occurring in these mice between 8 and 11 weeks of age, exercise accelerated this growth resulting in a greater increase in bone tissue over the 3 weeks of the study. Exercise increased tissue-level strain-to-failure and structural post-yield deformation in the male tibiae, but these post-yield benefits came at the expense of decreased yield deformation, structural and tissue-level yield strength and tissue-level ultimate strength. These results suggest that exercise superimposed upon growth accelerated growth-related increases in tibial cross-sectional dimensions. Exercise also influenced the quality of this forming bone, significantly impacting structural and tissue-level mechanical properties

Dual, orthogonal, backlit pinhole radiography in OMEGA experiments

Backlit pinhole radiography used with ungated film as a detector creates x-ray radiographs with increased resolution and contrast. Current hydrodynamics experiments on the OMEGA Laser use a three-dimensional sinusoidal pattern as a seed perturbation for the study of instabilities. The structure of this perturbation makes it highly desirable to obtain two simultaneous orthogonal backlighting views. We accomplished this using two backlit pinholes each mounted 12 mm12mm from the target. The pinholes, of varying size and shape, were centered on 5 mm5mm square foils of 50 μm50μm thick Ta. The backlighting is by KK-alpha emission from a 500 μm500μm square Ti or Sc foil mounted 500 μm500μm from the Ta on a plastic substrate. Four laser beams overfill the metal foil, so that the expanding plastic provides radial tamping of the expanding metal plasma. The resulting x-rays pass through the target onto (ungated) direct exposure film (DEF). Interference between the two views is reduced by using a nose cone in front of the DEF, typically with a 9 mm9mm Ta aperture and with magnets to deflect electrons. Comparison of varying types of pinholes and film exposures will be presented from recent experiments as well as an analysis of the background noise created using this experimental technique.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87894/2/10E327_1.pd

On Validating an Astrophysical Simulation Code

We present a case study of validating an astrophysical simulation code. Our study focuses on validating FLASH, a parallel, adaptive-mesh hydrodynamics code for studying the compressible, reactive flows found in many astrophysical environments. We describe the astrophysics problems of interest and the challenges associated with simulating these problems. We describe methodology and discuss solutions to difficulties encountered in verification and validation. We describe verification tests regularly administered to the code, present the results of new verification tests, and outline a method for testing general equations of state. We present the results of two validation tests in which we compared simulations to experimental data. The first is of a laser-driven shock propagating through a multi-layer target, a configuration subject to both Rayleigh-Taylor and Richtmyer-Meshkov instabilities. The second test is a classic Rayleigh-Taylor instability, where a heavy fluid is supported against the force of gravity by a light fluid. Our simulations of the multi-layer target experiments showed good agreement with the experimental results, but our simulations of the Rayleigh-Taylor instability did not agree well with the experimental results. We discuss our findings and present results of additional simulations undertaken to further investigate the Rayleigh-Taylor instability.Comment: 76 pages, 26 figures (3 color), Accepted for publication in the ApJ

Transition to turbulence and effect of initial conditions on three-dimensional compressible mixing in planar blast-wave-driven systems

Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh–Taylor, Richtmyer–Meshkov, and decompression effects. In this paper, results from three-dimensional (3D) numerical simulations of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams 9, 209 (1991)] are presented. Using the multiphysics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J. A. Greenough, J. Comput. Phys. 184, 53 (2003)], the late nonlinear instability evolution, including transition to turbulence, is considered for various multimode perturbation spectra. The 3D post-transition state differs from the 2D result, but the process of transition proceeds similarly in both 2D and 3D. The turbulent mixing transition results in a reduction in the growth rate of the mixing layer relative to its pretransition value and, in the case of the bubble front, relative to the 2D result. The post-transition spike front velocity is approximately the same in 2D and 3D. Implications for hydrodynamic mixing in core-collapse supernovae are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87764/2/056317_1.pd