Digital System Design Automation

Contains research objectives.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E

Elimination of leakage in GaN-on-diamond

The use of chemical vapor deposition diamond as a substrate for gallium nitride (GaN) to form GaN- on-diamond has the potential to allow for higher linear power densities in GaN high electron mobility transistors (HEMTs). The increase in GaN HEMT power density on diamond has been limited to date by the electrical leakage in GaN-on-diamond substrates. In this paper we show that to eliminate buffer leakage in silicon based GaN-on- diamond, you have to completely remove the transition layers used to grow high quality GaN on the original host silicon. By completely removing the transition layers in GaN-on-diamond, we demonstrated buffer leakage comparable to the leakage in GaN on silicon carbide

Hazard avoidance alerting with Markov decision processes

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004.Includes bibliographical references (p. 123-125).(cont.) (incident rate and unnecessary alert rate), the MDP-based logic can meet or exceed that of alternate logics.This thesis describes an approach to designing hazard avoidance alerting systems based on a Markov decision process (MDP) model of the alerting process, and shows its benefits over standard design methods. One benefit of the MDP method is that it accounts for future decision opportunities when choosing whether or not to alert, or in determining resolution guidance. Another benefit is that it provides a means of modeling uncertain state information, such as unmeasurable mode variables, so that decisions are more informed. A mode variable is an index for distinct types of behavior that a system exhibits at different times. For example, in many situations normal system behavior tends to be safe, but rare deviations from the normal increase the likelihood of a harmful incident. Accurate modeling of mode information is needed to minimize alerting system errors such as unnecessary or late alerts. The benefits of the method are illustrated with two alerting scenarios where a pair of aircraft must avoid collisions when passing one another. The first scenario has a fully observable state and the second includes an uncertain mode describing whether an intruder aircraft levels off safely above the evader or is in a hazardous blunder mode. In MDP theory, outcome preferences are described in terms of utilities of different state trajectories. In keeping with this, alerting system requirements are stated in the form of a reward function. This is then used with probabilistic dynamic and sensor models to compute an alerting logic (policy) that maximizes expected utility. Performance comparisons are made between the MDP-based logics and alternate logics generated with current methods. It is found that in terms of traditional performance measuresby Lee F. Winder.Ph.D

Analog Computer Research

Contains reports on two research projects

Évolution de l’économie politique des médias hongkongais

Pour la plupart des observateurs, la liberté de la presse à Hong Kong n’a cessé de reculer ces 15 dernières années. Cet article étudie la question de la liberté de la presse du point de vue de l’économie politique des médias. Il est communément admis que le gouvernement chinois a indirectement exercé son influence sur les médias hongkongais en cooptant les patrons de presse, pour la plupart des entrepreneurs ayant d’importants intérêts commerciaux sur le continent. Or le système politico-économique a connu simultanément des tensions internes et a donc ouvert un espace de résistance pour les professionnels des médias, aidant ainsi le système médiatique dans son ensemble à conserver un certain degré d’autonomie par rapport au centre du pouvoir. Au cours des années 2010 le paysage médiatique a cependant subi plusieurs transformations de taille, notamment la détérioration de l’environnement de l’industrie médiatique et l’essor des technologies des médias numériques. Ces mutations ont eu un impact sur la façon dont les patrons de presse calculent leur rapport coût-avantage, contribuant ainsi à l’arrivée de capitaux chinois dans le monde des médias hongkongais. Le secteur des médias numériques est lui aussi confronté au problème de l’ingérence de l’État chinois.Most observers argued that press freedom in Hong Kong has been declining continually over the past 15 years. This article examines the problem of press freedom from the perspective of the political economy of the media. According to conventional understanding, the Chinese government has exerted indirect influence over the Hong Kong media through co-opting media owners, most of whom were entrepreneurs with ample business interests in the mainland. At the same time, there were internal tensions within the political economic system. The latter opened up a space of resistance for media practitioners and thus helped the media system as a whole to maintain a degree of relative autonomy from the power centre. However, into the 2010s, the media landscape has undergone several significant changes, especially the worsening media business environment and the growth of digital media technologies. These changes have affected the cost-benefit calculations of media ownership and led to the entrance of Chinese capital into the Hong Kong media scene. The digital media arena is also facing the challenge of intrusion by the state

Changing Political Economy of the Hong Kong Media

Most observers argued that press freedom in Hong Kong has been declining continually over the past 15 years. This article examines the problem of press freedom from the perspective of the political economy of the media. According to conventional understanding, the Chinese government has exerted indirect influence over the Hong Kong media through co-opting media owners, most of whom were entrepreneurs with ample business interests in the mainland. At the same time, there were internal tensions within the political economic system. The latter opened up a space of resistance for media practitioners and thus helped the media system as a whole to maintain a degree of relative autonomy from the power centre. However, into the 2010s, the media landscape has undergone several significant changes, especially the worsening media business environment and the growth of digital media technologies. These changes have affected the cost-benefit calculations of media ownership and led to the entrance of Chinese capital into the Hong Kong media scene. The digital media arena is also facing the challenge of intrusion by the state

Cognitive Information Processing

Contains research objectives and reports on one research project.National Institutes of Health (Grant 1 PO1 GM-14940-01)National Institutes of Health (Grant 1 PO1 GM-15006-01)Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E