5,289 Works

Specification for a Real-Time Transport Protocol

Alfred Weaver, W Strayer & Bert Dempsey
Conventional standard transport protocols do not adequately support distributed real-time systems. An ideal protocol would ensure that at all times the communications subsystem is working on the task (message) of the most value to the overall system. In this paper we investigate how to develop a flexible and potent discrimination scheme based on importance, an abstract concept that measures the degree to which a task contributes to the overall system goal. We examine typical communication...

The WM Computer Architecture Definition and Rationale, Version 2

William Wulf

Starlite: An Environment for Distributed Database Prototyping

Sang Son & Jeremiah Ratner
One of the reasons for the difficulty in evaluating new techniques for distributed database systems is the complexity involved due to a large number of system parameters that may change dynamically. Prototyping methods can be applied effectively to the evaluation of database techniques. In addition, database technology can be implemented in a modular reusable form to enhance experimentation. This paper presents a software prototyping environment for the development and evaluation of distributed database systems. The...

The WM Computer Architecture

Wm Wulf

Code Generation for Streaming: an Access/Execute Mechanism

Manuel Benitez & Jack Davidson
Access/execute architectures have several advantages over more traditional architectures. Because address generation and memory access are decoupled from operand use, memory latencies are tolerated better, there is more potential for concurrent operation, and it permits the use of specialized hardware to facilitate fast address generation. This paper describes the code generation and optimization algorithms that are used in an optimizing compiler for an architecture that contains explicit hardware support for the access/execute model of computation....

WM Protection: The Base Mechanism

Wm Wulf & Anita Jones

A Study of the Effects of Subprogram Inlining

Anne Holler
This dissertation examines subprogram inlining, a widely-known code optimization technique whose effects were not well understood prior to this study. For a set of test programs on several computer systems, the sizes and runtimes of executable files produced using a tool that automatically substitutes subprograms inline were compared with those of versions in which call sites were not expanded inline. Issues raised by this experiment's results led to the formulation of equations hypothesized to estimate...

A Real-Time Synchronization Scheme for Replicated Data in Distributed Database Systems

Sang Son & Spiros Kouloumbis
The design and implementation of time-critical schedulers for real-time distributed replicated database systems must satisfy two major requirements: transactions must be able to meet the timing constraints associated with them, and mutual and internal consistency of replicated data must be preserved. In this paper, we propose a new replication control algorithm, which integrates real~time scheduling and replication control. The algorithm adopts a token-based scheme for replication control and attempts to balance the criticality of realtime...

Development of a Set of 'Closed Laboratories' for an Undergraduate Computer Science Curriculum

Wm Wulf
As a discipline, Computer Science has seen many dramatic changes in its brief history. Through new textbooks and an evolving curriculum, the content of undergraduate Computer Science education has for the most part kept pace with these changes. But the pedagogy has hardly changed. Not only is that pedagogy out of dat - - it is profoundly wrong. It emphasizes individual skill in writing short programs in a dead language, from scratch. This emphasis is...

Giving CANDY to Children: User-Tailored Gesture Input Driving An Articulator Based Speech Synthesizer

Randy Pausch & R Williams
The CANDY Project (Communication Assistance to Negate Disabilities in Youth) seeks to provide a realtime speech synthesizer for disabled individuals, particularly non-vocal children with cerebral palsy. Existing speech synthesizers convert user input into discrete linguistic or phonetic symbols which are converted into sound. Complicated sentences must be created by concatenating lower level symbols, precluding real-time conversational speech. We have developed an articulator-based speech synthesizer which simulates the motion of the human tongue and produces the...

An Environment for Integrating Architectural Design with Compiler Development

J Davidson & D Whalley

Distribute Algorithms for Efficient Deadlock Detection and Resolution

Yiechan Yang, Lifeng Hsu & S Son
In this paper we present two efficient distributed deadlock detection and resolution algorithms which combine both path-pushing and edge-chasing techniques to detect and resolve deadlocks in a distributed database system. By locally building up the PRAG (Partial Resource Allocation Graph)‘ information for every transaction on each site through edge - chasing and path-pushing, these algorithms _not only have transactions wait-for information but also have resources allocation information. Therefore, as soon as a deadlock cycle is...

Function-Driven Scheduling: A General Framework for Expression and Analysis of Scheduling

W Strayer
Scheduling theory maintains that there are fundamental similarities in problems of sequence that transcend the characteristics of the particular tasks to be ordered or the resources to be used. Traditionally, scheduling policies are implemented using algorithms; we study scheduling algorithms to discover the Various properties of the schedules they produce. To facilitate analysis the policies are typically limited to homogeneous task sets (e.g., all periodic tasks) and consider only one or very few task attributes....

Analysis of Deadline-Driven Scheduling Algorithms Using Function-Driven Techniques

W Strayer
Real-time systems must be responsive to task deadlines, hence deadlinedriven scheduling algorithms pervade real-time scheduling. Scheduling algorithms, whether for real-time system or not, often focus one or only a few of the task attributes or system characteristics for discriminating among competing tasks. The task set is comprised of tasks that either are dependent on the particular attributes or are forced to be. Expression of scheduling algorithms using function-driven techniques, in particular the importance abstraction [STRA92]...

After Suspicion

Rita Felski

After Magic: Modern Charm in History, Theory, and Practice

Herbert Tucker

Lower neighborhood quality in adolescence predicts higher mesolimbic sensitivity to reward anticipation in adulthood

Marlen Gonzalez, Joseph Allen & James Coan
Life history theory suggests that adult reward sensitivity should be best explained by childhood, but not current, socioeconomic conditions. In this functional magnetic resonance imaging (fMRI) study, 83 participants from a larger longitudinal sample completed the monetary incentive delay (MID) task in adulthood (∼25 years old). Parent-reports of neighborhood quality and parental SES were collected when participants were 13 years of age. Current income level was collected concurrently with scanning. Lower adolescent neighborhood quality, but...

A Synthetic Utilization Bound for Aperiodic Tasks with Resource Tequirements

Tarek Abdelzaher & Vivek Sharma
Utilization bounds for schedulability of aperiodic tasks are new in real-time scheduling literature. All aperiodic bounds known to date apply only to independent tasks. They either assume a liquid task model (one with infinitely many infinitesimal tasks) or are limited to deadline-monotonic and earliest-deadline first scheduling. In this paper, the authors make two important contributions. First, they derive the first aperiodic utilization bound that considers a task model with resource requirements. Second, the new bound...

Thomas Jefferson, Federalist

Peter Onuf

Parallel Genetic Algorithms with Local Search

CL Huntley & DE Brown
This paper presents methods of applying local search to global optimization problems. The most common approach, multistart, selects the best solution from restarts of local search from random starting points. Partitional methods augment local search with general principles concerning the location of global optima in real space, significantly improving the effectiveness of local search in function optimization problems. Standard partitional methods, however, are not directly applicable to combinatorial optimization problems. We describe a genetic algorithm,...

Resilience and recovery potential of duneland vegetation in the southern Kalahari

Abinash Bhattachan, Paolo D'Odorico, Kebonyethata Dintwe, Gregory Okin & Scott Collins
Many dune fields around the world have undergone alternating periods of mobilization and stabilization in response to changes in wind power and rainfall. However, in modern times disturbances associated with land use are believed to be a dominant factor contributing to the activation of stabilized vegetated dunes in drylands, while the reduction in human activities such as grazing and farming may lead to stabilization of once active dune fields. The Kalahari region of southern Africa...

PbSe quantum dot based luminescent solar concentrators

Dennis Waldron, Amanda Preske, Joseph Zawodny, Todd Krauss & Mool Gupta
The results are presented for luminescent solar concentrators (LSCs) fabricated with poly(lauryl methacrylate-co-ethylene glycol dimethacrylate) (P(LMA-co-EGDMA)) and Angstrom Bond, Inc. AB9093 acrylic epoxy matrix, high quantum yield (> 70%) PbSe quantum dots (QDs) and silicon photovoltaic (Si PV) cells. LSCs were tested under a lamp with broadband illumination, photon flux-matched to a standard solar spectrum and verified under a calibrated solar lamp source. The P(LMA-co-EGDMA) sample demonstrated the highest power conversion efficiency of any known...

Access Ordering Algorithms for a Multicopy Memory

Steven Moyer

The case for character displacement in plants

Carolyn Beans
The evidence for character displacement as a widespread response to competition is now building. This progress is largely the result of the establishment of rigorous criteria for demonstrating character displacement in the animal literature. There are, however, relatively few well-supported examples of character displacement in plants. This review explores the potential for character displacement in plants by addressing the following questions: (1) Why aren’t examples of character displacement in plants more common? (2) What are...


Rider Foley, Elise Barrella, Heather Kirkvold, Rodney Wilkins, Aaron Sloss, Elise Mazur, Claire Trevisan, Jacob Rogerson, Daniel Katleman, Catherine Mohan, Victoria Lindsey & Farrah Dang
The United States is in the midst of a transition in the production and distribution of energy. This transition was, in part, instigated by technological advancements and policy mechanisms that allowed for the recovery of unconventional fossil fuels from shale formations. In parallel, renewable energy sources such as wind and solar are becoming increasingly competitive with fossil fuels. Furthermore, the nation’s population is moving away from the Northeast and Midwest regions to southeastern and western...

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  • University of Virginia