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Full-Text Articles in Physical Sciences and Mathematics
Wait-Free And Obstruction-Free Snapshot, Khanh Do Ba
Wait-Free And Obstruction-Free Snapshot, Khanh Do Ba
Dartmouth College Undergraduate Theses
The snapshot problem was first proposed over a decade ago and has since been well-studied in the distributed algorithms community. The challenge is to design a data structure consisting of $m$ components, shared by upto $n$ concurrent processes, that supports two operations. The first, $Update(i,v)$, atomically writes $v$ to the $i$th component. The second, $Scan()$, returns an atomic snapshot of all $m$ components. We consider two termination properties: wait-freedom, which requires a process to always terminate in a bounded number of its own steps, and the weaker obstruction-freedom, which requires such termination only for processes that eventually execute uninterrupted. First, …
Computation Reuse In Statics And Dynamics Problems For Assemblies Of Rigid Bodies, Anne Loomis
Computation Reuse In Statics And Dynamics Problems For Assemblies Of Rigid Bodies, Anne Loomis
Dartmouth College Master’s Theses
The problem of determining the forces among contacting rigid bodies is fundamental to many areas of robotics, including manipulation planning, control, and dynamic simulation. For example, consider the question of how to unstack an assembly, or how to find stable regions of a rubble pile. In considering problems of this type over discrete or continuous time, we often encounter a sequence of problems with similar substructure. The primary contribution of our work is the observation that in many cases, common physical structure can be exploited to solve a sequence of related problems more efficiently than if each problem were considered …
Limited Delegation (Without Sharing Secrets) In Web Applications, Nicholas J. Santos
Limited Delegation (Without Sharing Secrets) In Web Applications, Nicholas J. Santos
Dartmouth College Undergraduate Theses
Delegation is the process wherein an entity Alice designates an entity Bob to speak on her behalf. In password-based security systems, delegation is easy: Alice gives Bob her password. This is a useful feature, and is used often in the real world. But it's also problematic. When Alice shares her password, she must delegate all her permissions, but she may wish to delegate a limited set. Also, as we move towards PKI-based systems, secret-sharing becomes impractical. This thesis explores one solution to these problems. We use proxy certificates in a non-standard way so that user Alice can delegate a subset …
Secure Context-Sensitive Authorization, Kazuhiro Minami
Secure Context-Sensitive Authorization, Kazuhiro Minami
Dartmouth College Ph.D Dissertations
Pervasive computing leads to an increased integration between the real world and the computational world, and many applications in pervasive computing adapt to the user's context, such as the location of the user and relevant devices, the presence of other people, light or sound conditions, or available network bandwidth, to meet a user's continuously changing requirements without taking explicit input from the users. We consider a class of applications that wish to consider a user's context when deciding whether to authorize a user's access to important physical or information resources. Such a context-sensitive authorization scheme is necessary when a mobile …
Path Planning Algorithms Under The Link-Distance Metric, David Phillip Wagner
Path Planning Algorithms Under The Link-Distance Metric, David Phillip Wagner
Dartmouth College Ph.D Dissertations
The Traveling Salesman Problem and the Shortest Path Problem are famous problems in computer science which have been well studied when the objective is measured using the Euclidean distance. Here we examine these geometric problems under a different set of optimization criteria. Rather than considering the total distance traversed by a path, this thesis looks at reducing the number of times a turn is made along that path, or equivalently, at reducing the number of straight lines in the path. Minimizing this objective value, known as the link-distance, is useful in situations where continuing in a given direction is cheap, …