Ion beam sputtering in electric propulsion facilities

Experiments were undertaken to determine sputter yields of potential ion beam target materials, to assess the impact of charge exchange on beam diagnostics in large facilities, and to examine material erosion and deposition after a 957 hr test of a 5 kW-class ion thruster. The xenon ion sputter yield of flexible graphite was lower than other graphite forms especially at high angles of incidence. Ion beam charge exchange effects were found to hamper beam probe current collection diagnostics even at pressures from 0.7 to 1.7 mPa. Estimates of the xenon ion beam envelope were made and predictions of the thickness of sputter deposited coatings in the facility were compared with measurements

Remaking Political Institutions: Climate Change and Beyond

This Element develops an original analytical foundation for studying institutional remaking and its political dynamics. It explains how institutional remaking can be observed and provides a typology comprising five areas of institutional production involved in institutional remaking (Novelty, Uptake, Dismantling, Stability, Interplay)

Backlash to Climate Policy

Hard climate policy (e.g., regulation, taxes/pricing, phaseouts) is needed to meet ambitious climate targets, but when such policy is introduced, it can sometimes trigger backlash. Backlash involves an abrupt and forceful negative reaction by a significant number of actors seeking to reverse a policy, often through extraordinary means that transgress established procedures and norms. Yet, explanations of policy backlash remain nascent and fragmented. I synthesize insights from within and beyond climate politics to argue that contested legitimacy is central to climate policy backlash, which provokes attempts toward delegitimation. I develop a conceptual pathway to explain the occurrence of climate policy backlash and generate hypotheses about how practices of delegitimation occur, and their effects. This contributes to explaining why backlash occurs, highlighting ideational factors alongside interests and institutions. Overall, I suggest the need for a contextually embedded approach to understanding the volatile dynamics of backlash, bringing political sociology into conversation with political economy

Natural laminar flow nacelle for transport aircraft

The potential of laminar flow nacelles for reducing installed engine/nacelle drag was studied. The purpose was twofold: to experimentally verify a method for designing laminar flow nacelles and to determine the effect of installation on the extent of laminar flow on the nacelle and on the nacelle pressure distributions. The results of the isolated nacelle tests illustrated that laminar flow could be maintained over the desired length. Installing the nacelles on wing/pylon did not alter the extent of laminar flow occurring on the nacelles. The results illustrated that a significant drag reduction was achieved with this laminar flow design. Further drag reduction could be obtained with proper nacelle location and pylon contouring

The evolutionary development of high specific impulse electric thruster technology

Electric propulsion flight and technology demonstrations conducted primarily by Europe, Japan, China, the U.S., and the USSR are reviewed. Evolutionary mission applications for high specific impulse electric thruster systems are discussed, and the status of arcjet, ion, and magnetoplasmadynamic thrusters and associated power processor technologies are summarized

Pelvic measurements and calving difficulty (1997)

Although researchers agree that birth weight is the most important measurable trait affecting calving difficulty, there is evidence that the size and shape of the pelvis also affect a heifer's ability to calve.New February 1997 -- Extension web site

Ion Thruster Development at NASA Lewis Research Center

Recent ion propulsion technology efforts at NASA's Lewis Research Center including development of kW-class xenon ion thrusters, high power xenon and krypton ion thrusters, and power processors are reviewed. Thruster physical characteristics, performance data, life projections, and power processor component technology are summarized. The ion propulsion technology program is structured to address a broad set of mission applications from satellite stationkeeping and repositioning to primary propulsion using solar or nuclear power systems

Development of arcjet and ion propulsion for spacecraft stationkeeping

Near term flight applications of arc jet and ion thruster satellite station-keeping systems as well as development activities in Europe, Japan, and the United States are reviewed. At least two arc jet and three ion propulsion flights are scheduled during the 1992-1995 period. Ground demonstration technology programs are focusing on the development of kW-class hydrazine and ammonia arc jets and xenon ion thrusters. Recent work at NASA LeRC on electric thruster and system integration technologies relating to satellite station keeping and repositioning will also be summarized

The Pathophysiology of Respiratory Failure in Chronic Obstructive Pulmonary Disease

The most important pathophysiologic aspects of chronic and acute obstructive pulmonary disease involve disturbances in ventilation with resulting derangement of gas exchange in the lung. There is considerable variability in the type of abnormality, the time of its appearance in relationship to the history of the disease, and in the progression of the abnormality in blood gases