Innovative electric propulsion thruster modeling

The objective of this program is to model and evaluate advanced nuclear electric propulsion (NEP) system concepts as an aid to the performance of NEP mission benefits studies. The two primary goals are as follows: (1) provide scaling relationships for mass, power, and efficiency, as functions of Isp, propellant type, and other important quantities. The discussion is presented in vugraph form

Advanced propulsion concepts

A variety of Advanced Propulsion Concepts (APC) is discussed. The focus is on those concepts that are sufficiently near-term that they could be developed for the Space Exploration Initiative. High-power (multi-megawatt) electric propulsion, solar sails, tethers, and extraterrestrial resource utilization concepts are discussed. A summary of these concepts and some general conclusions on their technology development needs are presented

Use of second formant transition and relative amplitude cues in labeling nasal place of articulation

Previous studies have shown that manipulation of the amplitude of a particular frequency region of the consonantal portion of a syllable relative to the amplitude of the same frequency region in an adjacent vowel influences the perception of place of articulation. This manipulation has been called the relative amplitude cue. The earlier studies examined the effect of the relative amplitude manipulation upon labeling place of articulation for fricatives and stop consonants. This current study looked at the influences of this manipulation upon labeling place of articulation for the /m/ - /n/ nasal distinction. Twenty-five listeners with normal hearing labeled nasal place of articulation for the synthetic syllables. Results show an influence of both relative amplitude and formant transition manipulation upon labeling behavior. These results add further evidence to the importance of acoustic boundaries in processing consonant place of articulation

The Greek philosophers against Arendt

Though Arendt was ambivalent about philosophy, much of her work shows careful and sustained engagement with ancient Greek philosophers, in particular Socrates, Plato and Aristotle. This article explores the distinctive ways in which Arendt uses these Greek philosophers, explains why she uses these philosophers in particular, and assesses whether her rethinking of the tradition of Western political thought they inaugurated on her view is coherent. I argue that Arendt's appropriation of their ideas puts a strain on her own account at various points; as she seeks to wrestle Socrates from Plato, and Aristotle from all essentialism, she raises questions about the trajectory and grounds of her own political theorizing. Since attention to the use of these thinkers exposes obscurities and tensions in her account, this article allows the Greek philosophers to fight back, by reading her deployment of them against her own theorizing

Is Your Lead Really Leading?

It\u27s your lead - but is anybody following? Do your words, like the aroma of fresh-baked bread, arouse the curiosity of readers and lead them to explore further

Comprehensive Tobacco Control Policy Regimes and Population Health: Assessing Causal Loops

Tobacco products remain among the most controversial consumer products of all time: cigarettes are the only legal product that, when used as intended, are lethal. The global and individual burden attributable to the primary use of tobacco, or secondary or tertiary exposure to cigarette smoke, whether measured by morbidity, mortality, or economic costs, is substantial. With the combined efforts of scientific research, public health and policy advocates, the image and use of tobacco products has undergone profound change. However, while much has been achieved regarding the attitudinal, behavioral, and policy changes needed to diminish the individual, social, and economic costs of tobacco use, much remains to be yet accomplished if these adverse tobacco use impacts are to be further curtailed. There is considerable evidence that tobacco use is becoming highly concentrated in lower socio-economic groups and that the rate of decline in smoking is slowing. Further, as the tobacco epidemic emerges in the developing world, there is considerable interest line applying the lessons learned in industrialized countries to developing countries, thereby truncating the tobacco epidemic and forgoing some of the enormous costs in countries least able to absorb such costs.;The unifying theme of the present work is an integration of the public health and political science perspectives on tobacco control so as to establish a more comprehensive framework of the underlying factors and elements interrelating tobacco use and tobacco control policy. A substantial challenge in developing such a framework is the complexity of the relationship between the two primary outcomes of interest. The relationships, including interdependencies and feedback mechanisms, are much more accurately characterized by a causal loop. This work presents an overview of the tobacco epidemic, a review of two very different literatures with different perspectives on the tobacco epidemic (public health literature and political and policy science), an empirical policy history analysis integrating the political and policy science viewpoint with the public health perspective on the evolution of the tobacco epidemic, and two quantitative analyses alternately supporting the interdependence and complex temporal relationship between tobacco control policy adoption and population health outcomes as well as the importance of societally-derived factors. An integrated conceptual model based on the causal loops of tobacco control policy and tobacco-related population health is then presented that incorporates the realms of population, governmental, judicial, public health, tobacco industry and other subsystems, and scientific communities. However, while this framework does assimilate the key elements and forces elucidated during the course of this work and integrates the political and policy science with the public health perspective, in truth this framework likely elicits more questions than it answers. The research questions and agendas and metrics proposed highlight both the strengths and deficiencies of the two perspectives

Using the Blues as a Teaching Tool

Off we go into the wild blue wonder! Blue wonder? Yes, that\u27s just how I felt today as I filled in the forms and sealed the envelope for another year\u27s shot at the blue

The NASA-JPL advanced propulsion program

The NASA Advanced Propulsion Concepts (APC) program at the Jet Propulsion Laboratory (JPL) consists of two main areas: The first involves cooperative modeling and research activities between JPL and various universities and industry; the second involves research at universities and industry that is directly supported by JPL. The cooperative research program consists of mission studies, research and development of ion engine technology using C-60 (Buckminsterfullerene) propellant, and research and development of lithium-propellant Lorentz-force accelerator (LFA) engine technology. The university/industry- supported research includes research (modeling and proof-of-concept experiments) in advanced, long-life electric propulsion, and in fusion propulsion. These propulsion concepts were selected primarily to cover a range of applications from near-term to far-term missions. For example, the long-lived pulsed-xenon thruster research that JPL is supporting at Princeton University addresses the near-term need for efficient, long-life attitude control and station-keeping propulsion for Earth-orbiting spacecraft. The C-60-propellant ion engine has the potential for good efficiency in a relatively low specific impulse (Isp) range (10,000 - 30,000 m/s) that is optimum for relatively fast (less than 100 day) cis-lunar (LEO/GEO/Lunar) missions employing near-term, high-specific mass electric propulsion vehicles. Research and modeling on the C-60-ion engine are currently being performed by JPL (engine demonstration), Caltech (C-60 properties), MIT (plume modeling), and USC (diagnostics). The Li-propellant LFA engine also has good efficiency in the modest Isp range (40,000 - 50,000 m/s) that is optimum for near-to-mid-term megawatt-class solar- and nuclear-electric propulsion vehicles used for Mars missions transporting cargo (in support of a piloted mission). Research and modeling on the Li-LFA engine are currently being performed by JPL (cathode development), Moscow Aviation Institute (engine testing), Thermacore (electrode development), as well as at MIT (plume modeling), and USC (diagnostics). Also, the mission performance of a nuclear-electric propulsion (NEP) Li-LFA Mars cargo vehicle is being modeled by JPL (mission analysis; thruster and power processor modeling) and the Rocketdyne Energy Technology and Engineering Center (ETEC) (power system modeling). Finally, the fusion propulsion research activities that JPL is supporting at Pennsylvania State University (PSU) and at Lawrenceville Plasma Physics (LPP) are aimed at far-term fast (less than 100 day round trip) piloted Mars missions and, in the very far term, interstellar missions