2,575 research outputs found

    Comet thermal modeling

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    The past year was one of tremendous activity because of the appearance of Halley's Comet. Observations of the comet were collected from a number of sources and compared with the detailed predictions of the comet thermal modeling program. Spacecraft observations of key physical parameters for cometary nucleus were incorporated into the thermal model and new cases run. These results have led to a much better understanding of physical processes on the nucleus and have pointed the way for further improvements to the modeling program. A model for the large-scale structure of cometary nuclei was proposed in which comets were envisioned as loosely bound agglomerations of smaller icy planetesimals, essentially a rubble pile of primordial dirty snowballs. In addition, a study of the physical history of comets was begun, concentrating on processes during formation and in the Oort cloud which would alter the volatile and nonvolatile materials in cometary nuclei from their pristine state before formation

    Investigations on the system boron-carbon silicon

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    The above elements form with each other binary compounds which are very interesting from the point of view of their structure and their chemistry and which are important for technology. The present investigation is concerned with the three-component system and the behavior of the binary compounds occurring in it. Investigations employing various techniques, such as X-ray, chemical analysis, microscopy and fusion experiments showed that no ternary phase exists within the boundary of the ternary system. There is no compound with a higher abrasion capacity than boron carbide. The probable phase field divisions at two isothermic intersections and the fusion isotherms are indicated

    Traumatic Brain Injury Recovery Care: Demand Forecasting, Staffing, and Treatment Planning

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    Improvised Explosive Device attacks have skyrocketed since the start of the War on Terror. Many troops wounded by these tactics receive long-lasting unseen wounds including Traumatic Brain Injury (TBI). TBI sufferers are treated along with other casualties. This has created an increasing, and varying, demand for ongoing post operative recovery care for troops returning from deployments. Diagnosis and treatment for TBI wounded troops is costly. This thesis is motivated by the recognition that budgets are constrained yet quality of care should not be compromised. Additive Holtz-Winters smoothing is used to forecast overall patient care demand, a regression based on queueing theory determines care consultant staffing levels, and reliability theory quantifies the idea of reducing cost by reducing parallel treatment planning. The scope is the Warfighter Rehabilitation Centers and AF Warrior and Survivor Care with data from SMEs, the Brookings Institution, and icasualties.org. This thesis provides a step-by-step methodology and analyzes the actual situation that leadership encountered from 2010-2012

    The direct synthesis of crosslinked polymeric azomethines

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    Char yields of synthesized crosslinked polymeric azomethine

    Understanding and Combating Investment Fraud

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    Investment fraud is a significant problem in America. Estimates vary, but a conservative one is that about 10 percent of the investors will be victimized by investment fraud at some point in their lives. Further, many baby boomers are entering retirement with significant assets, and enforcement actions by financial regulators indicate that investors can be vulnerable to fraud at key ‘wealth events’ in their lives, such as when they face a decision about what to do with money arising from the sale of a house, an inheritance, or an IRA rollover. Protecting these assets—for baby boomers and younger generations who face key wealth events—will be important to ensure the financial well-being and retirement security of millions of Americans. This chapter reviews the dynamics of investment fraud victimization, explains how fraudsters use social influence tactics to defraud their victims, and describes current investor protection efforts

    On a zero speed sensitive cellular automaton

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    Using an unusual, yet natural invariant measure we show that there exists a sensitive cellular automaton whose perturbations propagate at asymptotically null speed for almost all configurations. More specifically, we prove that Lyapunov Exponents measuring pointwise or average linear speeds of the faster perturbations are equal to zero. We show that this implies the nullity of the measurable entropy. The measure m we consider gives the m-expansiveness property to the automaton. It is constructed with respect to a factor dynamical system based on simple "counter dynamics". As a counterpart, we prove that in the case of positively expansive automata, the perturbations move at positive linear speed over all the configurations

    Softening of the insulating phase near Tc for the photo-induced insulator-to-metal phase transition in vanadium dioxide

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    We use optical-pump terahertz-probe spectroscopy to investigate the near-threshold behavior of the photoinduced insulator-to-metal (IM) transition in vanadium dioxide thin films. Upon approaching Tc a reduction in the fluence required to drive the IM transition is observed, consistent with a softening of the insulating state due to an increasing metallic volume fraction (below the percolation limit). This phase coexistence facilitates the growth of a homogeneous metallic conducting phase following superheating via photoexcitation. A simple dynamic model using Bruggeman effective medium theory describes the observed initial condition sensitivity.Comment: accepted for publication in Physical Review Letter
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