Access control, reverse access control and replication control in a world wide distributed system

In this paper we examine several access control problems that occur in an object-based distributed system that permits objects to be replicated on multiple machines. First, there is the classical access control problem, which relates to which users can execute which methods. Second, we identified a reverse access control problem, which concerns which replicas can execute which methods for authorized users. Finally, there is the issue of how updates are propagated securely from replica to replica. Our solution uses roles and preserves the scalability needed in a world-wide distributed system

Nanoparticle deposition in hydrogenated amorphous silicon films during rf plasma deposition

Particles of 2–14 nm diameter, representing 10(– 4)–10(– 3) of the film volume, are observed by scanning tunneling microscopy (STM) in thin films of hydrogenated amorphous silicon (a-Si:H) grown by rf-plasma-enhanced deposition using optimized conditions. The particles are produced in the discharge and incorporated in the film during growth, in contradiction to expected particle trapping by discharge sheath fields. The interfaces between the nanoparticles and the homogeneous film can produce low-density regions that form electronic defects in a-Si:H films

Surface roughening during plasma enhanced chemical vapor deposition of hydrogenated amorphous silicon on crystal silicon substrates.

The morphology of a series of thin films of hydrogenated amorphous silicon (a-Si:H) grown by plasma-enhanced chemical-vapor deposition (PECVD) is studied using scanning tunneling microscopy. The substrates were atomically flat, oxide-free, single-crystal silicon. Films were grown in a PECVD chamber directly connected to a surface analysis chamber with no air exposure between growth and measurement. The homogeneous roughness of the films increases with film thickness. The quantification of this roughening is achieved by calculation of both rms roughness and lateral correlation lengths of the a-Si:H film surface from the height difference correlation functions of the measured topographs. Homogeneous roughening occurs over the film surface due to the collective behavior of the flux of depositing radical species and their interactions with the growth surface

Towards a Flexible, Lightweight Virtualization Alternative

In recent times, two virtualization approaches have become dominant: hardware-level and operating system-level virtualization. They differ by where they draw the virtualization boundary between the virtualizing and the virtualized part of the system, resulting in vastly different properties. We argue that these two approaches are extremes in a continuum, and that boundaries in between the extremes may combine several good properties of both. We propose abstractions to make up one such new virtualization boundary, which combines hardware-level flexibility with OS-level resource sharing. We implement and evaluate a first prototype

Construction of silicon nanocolumns with the scanning tunneling microscope

Voltage pulses to a scanning tunneling microscope (STM) are used to construct silicon columns of 30–100 Å diameter and up to 200 Å height on a silicon surface and on the end of a tungsten probe. These nanocolumns have excellent conductivity and longevity, and they provide an exceptional new ability to measure the shapes of nanostructures with a STM. This construction methodology and these slender yet robust columns provide a basis for nanoscale physics, lithography, and technology

A model-theoretic interpretation of environmentally-induced superselection

Environmentally-induced superselection or "einselection" has been proposed as an observer-independent mechanism by which apparently classical systems "emerge" from physical interactions between degrees of freedom described completely quantum-mechanically. It is shown that einselection can only generate classical systems if the "environment" is assumed \textit{a priori} to be classical; einselection therefore does not provide an observer-independent mechanism by which classicality can emerge from quantum dynamics. Einselection is then reformulated in terms of positive operator-valued measures (POVMs) acting on a global quantum state. It is shown that this re-formulation enables a natural interpretation of apparently-classical systems as virtual machines that requires no assumptions beyond those of classical computer science.Comment: 15 pages, 1 figure; minor correction

Efficient routing on complex networks

In this letter, we propose a new routing strategy to improve the transportation efficiency on complex networks. Instead of using the routing strategy for shortest path, we give a generalized routing algorithm to find the so-called {\it efficient path}, which considers the possible congestion in the nodes along actual paths. Since the nodes with largest degree are very susceptible to traffic congestion, an effective way to improve traffic and control congestion, as our new strategy, can be as redistributing traffic load in central nodes to other non-central nodes. Simulation results indicate that the network capability in processing traffic is improved more than 10 times by optimizing the efficient path, which is in good agreement with the analysis.Comment: 4 pages, 4 figure