1,490 research outputs found
The practice of crime prevention: design principles for more effective security governance
South Africa has had a comprehensive crime prevention policy agenda for some time in the form of the 1996 National Crime Prevention Strategy and the 1998 White Paper on Safety and Security. Despite this, prevention has remained very much a second cousin within the South African criminal justice family, notwithstanding the fact that there is widespread agreement that it warrants far more attention. In this article we briefly review some of the principal obstacles to effective crime prevention. Our understanding of âcrime preventionâ is a broad one â it involves simply asking the question: How can we reduce the likelihood of this happening again? This question opens up a range of preventative possibilities. Whether they are of a socio-economic, environmental or law enforcement nature depends on the nature of the (crime) problem. On the basis of our analysis, we propose three design principles to be followed if we, South Africans are to establish crime prevention as a central focus of our security governance. These design principles articulate what might be thought of as âbest thinkingâ rather than âbest practiceâ
Batteries: Imaging degradation
The degradation and failure of Li-ion batteries is strongly associated with electrode microstructure change upon (de)lithiation. Now, an operando X-ray tomography approach is shown to correlate changes in the microstructure of electrodes to cell performance, and thereby predict degradation pathways
On the origin and application of the Bruggeman correlation for analysing transport phenomena in electrochemical systems
The widely used Bruggeman equations correlate tortuosity factors of porous media with their porosity. Finding diverse application from optics to bubble formation, it received considerable attention in fuel cell and battery research, recently. The ability to estimate tortuous mass transport resistance based on porosity alone is attractive, because direct access to the tortuosity factors is notoriously difficult. The correlation, however, has limitations, which are not widely appreciated owing to the limited accessibility of the original manuscript. We retrace Bruggeman's derivation, together with its initial assumptions, and comment on validity and limitations apparent from the original work to offer some guidance on its use
TauFactor: An open-source application for calculating tortuosity factors from tomographic data
TauFactor is a MatLab application for efficiently calculating the tortuosity factor, as well as volume fractions, surface areas and triple phase boundary densities, from image based microstructural data. The tortuosity factor quantifies the apparent decrease in diffusive transport resulting from convolutions of the flow paths through porous media. TauFactor was originally developed to improve the understanding of electrode microstructures for batteries and fuel cells; however, the tortuosity factor has been of interest to a wide range of disciplines for over a century, including geoscience, biology and optics. It is still common practice to use correlations, such as that developed by Bruggeman, to approximate the tortuosity factor, but in recent years the increasing availability of 3D imaging techniques has spurred interest in calculating this quantity more directly. This tool provides a fast and accurate computational platform applicable to the big datasets (>10^8 voxels) typical of modern tomography, without requiring high computational power
Trends In Mathematics Enrollment And Achievement Gap In St. Louis Area Public High Schools, 2000 - 2014.
Long before the âNo Child Left Behindâ, Elementary and Secondary Education Act of 1965, or Brown vs. Board of Education, students of color have dreamed and struggled for equity in education. The issue of equal access to high quality of education highlighted in the NCLB focused public attention on the racial achievement gap. The present study examined mathematics enrollment and achievement trends among St. Louis area public high school students from 2000 to 2014 The study compared the results among racial groups and by gender rather than using a traditional Black-White comparison. Several frameworks contributed to the development of the study: Critical Race Theory, Effectively Maintained Inequality and Whiteness as property. Although the findings showed that enrollment in advanced mathematics classes and the number of students taking ACT tests increased across the racial groups, the results also indicated inequities in access to Advanced Placement classes, and level of college readiness. In conclusion, there is a little change in providing equitable access to advanced levels of mathematics with students who need it most receiving the least help and therefore remain far from closing the achievement gap
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