43,159 research outputs found
Study of limit cycles and stability of a space vehicle attitude control system
Limit cycles and stability of three-axis space vehicle attitude control syste
Open-celled polyurethane foam
Open-celled polyurethane foam has a density of 8.3 pounds per cubic foot and a compressive strength of 295 to 325 psi. It is useful as a porous spacer in layered insulation and as an insulation material in vacuum tight systems
Strangers in Arms: Combat Motivation in the Canadian Army, 1943-1945 (Book Review) by Robert Engen
Review of Strangers in Arms: Combat Motivation in the Canadian Army, 1943-1945 by Robert Engen
Solving California's Dropout Crisis
Synthesizes ongoing CDRP research to outline the scope, the causes, and the costs of the state's high school dropout crisis. Proposes a policy agenda to raise the graduation rate, with separate recommendations for the state, districts, and schools
Evidence-Based Practice and Organizational Development in Libraries
This article is written for a Festschrift for F. W. Lancaster, and it
summarizes the author???s library school experiences as a student of
Professor Lancaster and Professor Herbert Goldhor at the University
of Illinois. Both professors instilled in students a strong inclination
to use real and appropriate information in evaluating situations,
making decisions, delivering information services, and managing
libraries. The author suggests that this Lancaster-Goldhor approach
to information, and to data-driven decision making, anticipated the
current movement toward evidence-based practice (EBP) in libraries.
He suggests that libraries embrace the premises, philosophy, values,
and practices of organizational development (OD) as an overarching
discipline that facilitates EBP in the library culture, and ultimately
leads to healthier and more effective organizations. This article
complements a 2004 Library Trends article on OD, and numerous
recent publications on OD and related topics are cited.published or submitted for publicatio
Invisible Scars: Mental Trauma and the Korean War (Book Review) by Meghan Fitzpatrick
Review of Invisible Scars: Mental Trauma and the Korean War by Meghan Fitzpatrick
NASAs Plans for Development of Standards for Additive Manufactured Components
There are currently no NASA standards providing specific design and construction requirements for certification of additively manufactured parts. Several international standards organizations are developing standards for additive manufacturing; however, NASA mission schedules preclude the Agency from relying on these organizations to develop standards that are both timely and applicable. NASA and its program partners in manned spaceflight (the Commercial Crew Program, the Space Launch System and the Orion Multi-purpose Crew Vehicle) are actively developing additively manufactured parts for flight as early as 2018. To bridge this gap, NASA Marshall Space Flight Center (MSFC) has authored a center-level standard (MSFC-STD-3716)1 to establish standard practices for the Laser Powder Bed Fusion (L-PBF) process. In its draft form, the MSFC standard has been used as a basis for L-PBF process implementation for each of the manned space flight programs. The development of an Agency-level standard is proposed, which based upon the principles of MSFC-STD-3716, would have application to multiple additive manufacturing processes and be readily adaptable to all NASA programs
Laboratory investigations
Laboratory studies related to cometary grains and the nuclei of comets can be broken down into three areas which relate to understanding the spectral properties, the formation mechanisms, and the evolution of grains and nuclei: (1) Spectral studies to be used in the interpretation of cometary spectra; (2) Sample preparation experiments which may shed light on the physical nature and history of cometary grains and nuclei by exploring the effects on grain emissivities resulting from the ways in which the samples are created; and (3) Grain processing experiments which should provide insight on the interaction of cometary grains with the environment in the immediate vicinity of the cometary nucleus as the comet travels from the Oort cloud through perihelion, and perhaps even suggestions regarding the relationship between interstellar grains and cometary matter. A summary is presented with a different view of lab experiments than is found in the literature, concentrating on measurement techniques and sample preparations especially relevant to cometary dust
Dynamic crystallization of silicate melts
Two types of furnaces with differing temperature range capabilities were used to provide variations in melt temperatures and cooling rates in a study of the effects of heterogeneous nucleation on crystallization. Materials of chondrule composition were used to further understanding of how the disequilibrium features displayed by minerals in rocks are formed. Results show that the textures of natural chondrules were duplicated. It is concluded that the melt history is dominant over cooling rate and composition in controlling texture. The importance of nuclei, which are most readily derived from preexisting crystalline material, support an origin for natural chondrules based on remelting of crystalline material. This would be compatible with a simple, uniform chondrule forming process having only slight variations in thermal histories resulting in the wide range of textures
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