Attached and separated boundary layers on highly cooled, ablating and nonablating models at M equals 13.8

Attached and separated boundary layers on highly cooled, ablating and nonablating models at Mach 13.

Uniform Silicon Isotope Ratios Across the Milky Way Galaxy

We report the relative abundances of the three stable isotopes of silicon, $^{28}$Si, $^{29}$Si and $^{30}$Si, across the Galaxy using the $v = 0, J = 1 \to 0$ transition of silicon monoxide. The chosen sources represent a range in Galactocentric radii ($R_{\rm GC}$) from 0 to 9.8 kpc. The high spectral resolution and sensitivity afforded by the GBT permit isotope ratios to be corrected for optical depths. The optical-depth-corrected data indicate that the secondary-to-primary silicon isotope ratios $^{29}{\rm Si}/^{28}{\rm Si}$ and $^{30}{\rm Si}/^{28}{\rm Si}$ vary much less than predicted on the basis of other stable isotope ratio gradients across the Galaxy. Indeed, there is no detectable variation in Si isotope ratios with $R_{\rm GC}$. This lack of an isotope ratio gradient stands in stark contrast to the monotonically decreasing trend with $R_{\rm GC}$ exhibited by published secondary-to-primary oxygen isotope ratios. These results, when considered in the context of the expectations for chemical evolution, suggest that the reported oxygen isotope ratio trends, and perhaps that for carbon as well, require further investigation. The methods developed in this study for SiO isotopologue ratio measurements are equally applicable to Galactic oxygen, carbon and nitrogen isotope ratio measurements, and should prove useful for future observations of these isotope systems.Comment: 18 pages, 12 figures, 2 tables. Published in The Astrophysical Journal, Volume 839, Issue

The Relationship Between the Employment of School Resource Officers, School Discipline, and School-Based Arrests Variables

The school resource officer (SRO) program is a program developed in the United States with the goal of making schools a safer environment for students across all grades (Cray & Weiler, 2011). To date, the majority of research surrounding SRO programs focuses on recommended characteristics and qualities of SROs, as well as appropriate utilization of SROs (Weiler & Cray, 2011). However, relatively little is known about the effect of increased presence of SRO’s in the school setting. With SRO’s being tasked with disciplinarian roles Barnes (2016), it would be important to look at the effect of SRO’s on school discipline variables such as out-of-school suspension (OSS). With OSS being linked to increased risk for arrest (Theriot, 2009), it would be important to analyze the effect of these variables on each other. Taking it one step further, minority populations are typically disciplined at a higher rate than their white peers (Okonofua & Eberhardt, 2015). The purpose of this study is to examine the increased presence of SRO’s, OSS and minority and their effect on school-based arrest. The results support previous research in finding that OSS and number of SRO’s employed were significant predictors of school-based arrest. However, percentage of minority population was not found to be a predictor of school-based arrest. More research is needed to understand the extent of the relationship between OSS, SRO’s, and school-based arrests and how it might be possible to reduce this connection

A nonintrusive laser interferometer method for measurement of skin friction

A method is described for monitoring the changing thickness of a thin oil film subject to an aerodynamic shear stress using two focused laser beams. The measurement is then simply analyzed in terms of the surface skin friction of the flow. The analysis includes the effects of arbitrarily large pressure and skin friction gradients, gravity, and time varying oil temperature. It may also be applied to three dimensional flows with unknown direction. Applications are presented for a variety of flows including two dimensional flows, three dimensional swirling flows, separated flow, supersonic high Reynolds number flows, and delta wing vortical flows

Évaluation économique des programmes de remplacement de la main d’oeuvre expatriée dans les pays en voie de développement : étude du cas de la Côte-d’Ivoire

This study addresses several problems of educational policy posed by the replacement of highly skilled expatriates in the Ivory Coast's labor force. Conceptualizing expatriate replacement as an import-substitution activity in which Ivorian labor substitutes for previously imported labor services, the authors apply a modified Domestic Resource Cost (DRC) analysis to evaluate Ivorian secondary and university educational programs necessary to train the local labor.This methodology, along with more conventional cost-benefit approach, confirms that education is economically desirable in the Ivory Coast and that resource allocation to the upper secondary level is especially warranted. Lower secondary education is useful in so far as it performs a conduit function for higher levels of training. The importance of university education will probably increase as the occupational-educational structure is upgraded through technological development. Finally, consideration should be given to instituting a system of tuition charges in order to equate social and private rates of return in upper secondary and university education

Skin Friction Measurements by a Dual-Laser-Beam Interferometer Technique

A portable dual-laser-beam interferometer that nonintrusively measures skin friction by monitoring the thickness change of an oil film subject to shear stress is described. The method is an advance over past versions in that the troublesome and error-introducing need to measure the distance to the oil leading edge and the starting time for the oil flow has been eliminated. The validity of the method was verified by measuring oil viscosity in the laboratory, and then using those results to measure skin friction beneath the turbulent boundary layer in a low speed wind tunnel. The dual-laser-beam skin friction measurements are compared with Preston tube measurements, with mean velocity profile data in a "law-of-the-well" coordinate system, and with computations based on turbulent boundary-layer theory. Excellent agreement is found in all cases. (This validation and the aforementioned improvements appear to make the present form of the instrument usable to measure skin friction reliably and nonintrusively in a wide range of flow situations in which previous methods are not practical.

Student Voices: Recording the First-Generation Experience

In this session, an English instructor, digital initiatives librarian, and archivist at the University of Northern Colorado (UNC) will discuss an inter-departmental collaboration that integrates a digital story-telling project into undergraduate instruction. This project focuses on first-generation students, a population that is growing at colleges and universities across the nation. At UNC, approximately 40% of the undergraduate population is classified as first-generation. The UNC Libraries has partnered with the Center for Human Enrichment, which provides support for first-generation students through instruction, tutoring, and advising, to develop the Student Voices project. This innovative collaboration captures oral histories documenting the first-generation freshman experience and makes them available via the Libraries’ digital repository. The goal of the project is twofold: to document the perspectives and experiences of first-generation students, which have been largely absent within the university historical record, while simultaneously delivering instruction in primary sources and archives. The project is delivered as a classroom assignment, with the resulting student-recorded oral histories collected by the UNC Archives and Special Collections and placed in the digital repository. The session will offer a case study that covers both digital initiatives in undergraduate instruction and interdisciplinary collaboration between campus units. The presenters will explore issues of teaching, engaging, and incorporating digital initiative concepts into undergraduate education and will talk about the project goals, lesson plan, learning outcomes, technical aspects, and lessons learned. Attendees will receive ideas for implementing similar collaborations at their institutions

Regular Incidence Complexes, Polytopes, and C-Groups

Regular incidence complexes are combinatorial incidence structures generalizing regular convex polytopes, regular complex polytopes, various types of incidence geometries, and many other highly symmetric objects. The special case of abstract regular polytopes has been well-studied. The paper describes the combinatorial structure of a regular incidence complex in terms of a system of distinguished generating subgroups of its automorphism group or a flag-transitive subgroup. Then the groups admitting a flag-transitive action on an incidence complex are characterized as generalized string C-groups. Further, extensions of regular incidence complexes are studied, and certain incidence complexes particularly close to abstract polytopes, called abstract polytope complexes, are investigated.Comment: 24 pages; to appear in "Discrete Geometry and Symmetry", M. Conder, A. Deza, and A. Ivic Weiss (eds), Springe

Phase coexistence of cluster crystals: beyond the Gibbs phase rule

We report a study of the phase behavior of multiple-occupancy crystals through simulation. We argue that in order to reproduce the equilibrium behavior of such crystals it is essential to treat the number of lattice sites as a constraining thermodynamic variable. The resulting free-energy calculations thus differ considerably from schemes used for single-occupancy lattices. Using our approach, we obtain the phase diagram and the bulk modulus for a generalized exponential model that forms cluster crystals at high densities. We compare the simulation results with existing theoretical predictions. We also identify two types of density fluctuations that can lead to two sound modes and evaluate the corresponding elastic constants.Comment: 4 pages, 3 figure