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JenaMarie Baldaino MS Danica M. Ommen PhD Christopher P. Saunders PhD Jack Hietpas PhD JoAnn Buscaglia PhD 《Journal of forensic sciences》2021,66(1):83-95
Aluminum (Al) powders are commonly used in improvised explosive devices as metallic fuels, a component of explosive mixtures. These powders can be obtained readily from industrial‐scale and consumer products, and produced using unsophisticated “kitchen chemistry” techniques. This research demonstrates the potential of automated particle micromorphometry for comparisons between known source and questioned Al powders recovered from IEDs, as well as for insight into the method of Al powder manufacture. Al powder samples were obtained from legitimate manufacturers, and 56 samples were produced “in‐house” from Al‐containing spray paints and ball‐milled Al foils. Transmitted light microscope images of Al powder particles were acquired using an automated stage with automated z‐focus; 17 size and shape parameters were measured for all particles. Approximately 37,000–2,500,000 particles/sample were analyzed using an open‐source statistical package with customized code. Dimensionality reduction was required for processing the large datasets: eight of the 17 measured variables were selected based on inspection of the correlation matrix. Data from four subsamples from each of the 56 samples produced using “in‐house” methods were analyzed using ANOVA to assess the within‐ and between‐sample variation. High within‐sample variation was noted; however, ANOVA and post‐hoc Tukey's honestly significant difference (HSD) tests demonstrated that the between‐sample variation was substantially larger than the within‐sample variation. Each sample could be differentiated from all other samples in the test set. Future experiments will focus on ways to reduce the within‐sample variation, and additional statistical and microanalytical methods to classify sources and confidently constrain the method of Al powder manufacture. 相似文献
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Jack Scarborough 《政策研究评论》1991,10(2-3):12-30
This paper documents the decision process pursued by the President and key federal agencies addressing the issue of privatization of routine commercial space satellite launches via expendable launch vehicles. It is a case study of incremental decision making in the extreme, characterized by the formulation of conflicting policy goals in response to contingencies which ultimately paralyzed the policy process, even as government was confronted with issues of considerable gravity and urgency. The decision process unfolded in a highly dynamic environment, including the development of a internationally competitive space launch market and the Challenger accident. A key issue is the role of the chief executive in managing the policy implementation process, once conflicting goals have been formulated. The case illustrates how strategic miscalculation by the agencies involved, and a laissez-faire management style by the chief executive, exacerbate the ordinarily expected difficulties. 相似文献
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The conflicts in the formerly united Sudan have led to millions of deaths since the country's independence. The Naivasha Agreement was meant to end these wars. The January 2005 agreement foresaw a future where the Sudan People's Liberation Army/Movement and the Sudanese government would coexist within the framework of a united country. Subsequently, in 2011, however, the country was partitioned and the conflicts in Sudan and South Sudan have continued unabated. Interrogating the treaty texts and employing a case study approach and analysis of the economic and power dynamics within the region, this paper addresses the reason behind the failure of the comprehensive peace agreement and subsequent agreements intended to bring peace after partition. It becomes evident that the same dynamics that fed the partition of the country have helped bring conflict within its two successor states. In short, agreements are not sufficient to build peace. 相似文献
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