Sequential nature of damage annealing and activation in implanted GaAs

Rapid thermal processing of implanted GaAs reveals a definitive sequence in the damage annealing and the electrical activation of ions. Removal of implantation-induced damage and restoration of GaAs crystallinity occurs first. Irrespective of implanted species, at this stage the GaAs is n-type and highly resistive with almost ideal values of electron mobility. Electrical activation is achieved next when, in a narrow anneal temperature window, the material becomes n- or p-type, or remains semi-insulating, commensurate to the chemical nature of the implanted ion. Such a two-step sequence in the electrical doping of GaAs by ion implantation may be unique of GaAs and other compound semiconductors

Activation analysis of rapid thermally annealed Si and Mg implanted semi-insulating GaAs

Electronic properties of Si and Mg implants in undoped semi-insulating GaAs are studied. The activation of the implants is achieved by rapid thermal annealing. The effects of implantation dose and anneal temperature on the measured electrical activity are investigated. In spite of similar depth distributions and implantation damage characteristics, a marked difference between the activations of the Si and the Mg ions is observed for the dose range considered (3×10^12 – 1×10^14 cm^–2). Lattice strain measurements performed by x-ray rocking curves indicate that the residual implantation damage after annealing is not largely responsible for this difference. The difference is mostly electronic in character, as also suggested by photoluminescence measurements. At high annealing temperatures, changes in the compensating properties of undoped semi-insulating GaAs are suspected, and are found to play an important role in the activation of implanted ions, affecting the n- and p-type dopants conversely

A technoregulatory analysis of government regulation and oversight in the United States for the protection of passenger safety in commercial human spaceflight

Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis. Vita.Includes bibliographical references (p. 80-91).Commercial human spaceflight looks ready to take off as an industry, with "space tourism" as its first application. Paying passengers are likely to begin taking suborbital spaceflights within the next several years, both despite and because of the risks and hazards inherent in human spaceflight. As this activity poses dangers to passengers, there will be an increasing degree of government regulation and oversight to protect participant safety. Though human spaceflight is not a new endeavour, commercial human spaceflight poses a new set of challenges for regulators to grapple with. As is the case with many emerging technological industries, the regulatory challenge is to protect the safety of both participants and the uninvolved without regulating to a degree that stifles industry innovation and growth. This thesis examines the history and regulation of commercial human spaceflight to date. The technical background, systems engineering, and risk management of human spaceflight are explored, to determine which particular subsystem-mission phase combinations warrant closer regulatory attention. Finally, this paper gives recommendations on how future regulation of this nascent industry ought to be approached by the federal government and its regulatory agencies.by Michael Elliot Leybovich.S.M.S.M.in Technology and Polic

“I Had a Document in the Form of a Pass in German…”: An Incident from the Life of Soviet Prisoners of War in 1941

On the basis of published and archival ego-documents, the article reconstructs the stories of military medical assistant Timofei M. Malygin and junior lieutenant of the Red Army Vladimir S. Nyrkin who were held captive by the Germans for a short period of time in 1941–42. These stories are of interest because in addition to the event-related aspect associated with the captivity of the Red Army commanders and their subsequent escape, there are hidden mental structures of the narrative: fatalism, high level of adaptability to circumstances, willpower, enterprise, ability to find non-standard solutions, and rejection of any kind of racial superiority and humiliation. The article consists of 5 main sections and brief conclusions. In the first section, the authors characterize the explanatory concept adopted by them within the framework of the anthropological perspective of historical knowledge. We were interested in particular instances that allow us to see what cannot be descried in a universal historical perspective: characteristic features of time and place, people’s actions and relationships described by those people. The article focuses on the participation of both main characters in helping the wounded Soviet prisoners of war. The second section contains a brief historiographical overview of the subject of and presents methods for working with sources, among which are the records of interrogations of Vladimir S. Nyrkin and Timofei M. Malygin in the investigative bodies of the NKVD. Three subsequent sections reveal the stages of being in captivity: the act of being taken captive, being held in captivity, and escape. The conclusion summarizes the results of the study. Despite their privileged position, the Red Army commanders fled from the camp at the first opportunity: V. Nyrkin established contact with the partisans, and T. Malygin used available material resources and exchanged valuables and money for the local residents’ services necessary for the escape. Authentic German documents related to the topic are presented in the article in the form of illustrations: a “passport” handwritten by a German military doctor and a typewritten “Ausweis” signed by the commandant of the transit camp for prisoners of war in the city of Smolensk

Identifying the Dynamics of Technology Transition: ADS-B Adoption in the National Airspace System

Congestion is a growing problem in the National Airspace System (NAS). Predictions indicate that the NAS, as a whole, will be operating at 75% of capacity by 2010 [2] and that the demand in capacity in air transportation will double within a span of 10 to 35 years [3]. In order for the U.S. to maintain leadership in air transportation and meet the challenges of demand and efficiency of the 21st century, the NAS infrastructure, technology, and procedural strategies need to be modernized [4]. To this end, the FAA plans to implement a cooperative surveillance system called Automatic Dependent Surveillance -- Broadcast, or ADS-B. The surveillance technology and its applications are expected to provide important operational improvements by addressing some of the limitations of the current surveillance system

On the implementation of a recently proposed dosimetric formalism to a robotic radiosurgery system

The aim of this work is to implement a recently proposed dosimetric formalism for nonstandard fields to the calibration and small field output factor measurement of a robotic stereotactic radiosurgery system

Dosimetry tools and techniques for IMRT

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98734/1/MPH001313.pd

Too big to fail — lessons for today and the future from British industrial policy, 1960–1990

British industrial policy for two sectors (automotive and aerospace manufacture) in the period the 1960–1990 is considered and compared with the challenges facing the United Kingdom following the financial crisis of 2008. The history of the period 1960–1990 is informed by interviews with well-placed policy-makers of the time. These observations complement the historical record to confirm that British industrial policy was then more often a pragmatic response to events than the consequence of political ideology. Four particular phases of policy are observed: consolidation, investment, nationalisation and privatisation. During the decade 2000–2009 several British companies in banking, transport and energy have been subject to similar state interventions. In 2010 these companies are at various stages on the four step journey considered by the paper. The paper provides four lessons from the past for twenty-first century policy makers tasked with taking forward the companies with state investment and ensuring a return to economic prosperity