Brown University

About: Brown University is a education organization based out in Providence, Rhode Island, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 35778 authors who have published 90896 publications receiving 4471489 citations. The organization is also known as: brown.edu & Brown.

H-store: a high-performance, distributed main memory transaction processing system

Abstract: Our previous work has shown that architectural and application shifts have resulted in modern OLTP databases increasingly falling short of optimal performance [10]. In particular, the availability of multiple-cores, the abundance of main memory, the lack of user stalls, and the dominant use of stored procedures are factors that portend a clean-slate redesign of RDBMSs. This previous work showed that such a redesign has the potential to outperform legacy OLTP databases by a significant factor. These results, however, were obtained using a bare-bones prototype that was developed just to demonstrate the potential of such a system. We have since set out to design a more complete execution platform, and to implement some of the ideas presented in the original paper. Our demonstration presented here provides insight on the development of a distributed main memory OLTP database and allows for the further study of the challenges inherent in this operating environment.

Performing Remains: Art and War in Times of Theatrical Reenactment

Abstract: 'At last, the past has arrived! Performing Remains is Rebecca Schneider's authoritative statement on a major topic of interest to the field of theatre and performance studies. It extends and consolidates her pioneering contributions to the field through its interdisciplinary method, vivid writing, and stimulating polemic. Performing Remains has been eagerly awaited, and will be appreciated now and in the future for its rigorous investigations into the aesthetic and political potential of reenactments.' - Tavia Nyong'o, Tisch School of the Arts, New York University 'I have often wondered where the big, important, paradigm-changing book about re-enactment is: Schneider’s book seems to me to be that book. Her work is challenging, thoughtful and innovative and will set the agenda for study in a number of areas for the next decade.' - Jerome de Groot, University of Manchester Performing Remains is a dazzling new study exploring the role of the fake, the false and the faux in contemporary performance. Rebecca Schneider argues passionately that performance can be engaged as what remains, rather than what disappears. Across seven essays, Schneider presents a forensic and unique examination of both contemporary and historical performance, drawing on a variety of elucidating sources including the "America" plays of Linda Mussmann and Suzan-Lori Parks, performances of Marina Abramovic´ and Allison Smith, and the continued popular appeal of Civil War reenactments. Performing Remains questions the importance of representation throughout history and today, while boldly reassessing the ritual value of failure to recapture the past and recreate the "original."

Space weathering on airless bodies: Resolving a mystery with lunar samples

Abstract: — Using new techniques to examine the products of space weathering of lunar soils, we demonstrate that nanophase reduced iron (npFe0) is produced on the surface of grains by a combination of vapor deposition and irradiation effects. The optical properties of soils (both measured and modeled) are shown to be highly dependent on the cumulative amount of npFe0, which varies with different starting materials and the energetics of different parts of the solar system. The measured properties of intermediate albedo asteroids, the abundant S-type asteroids in particular, are shown to directly mimic the effects predicted for small amounts of npFe0 on grains of an ordinary chondrite regolith. This measurement and characterization of space weathering products seems to remove a final obstacle hindering a link between the abundant ordinary chondrite meteorites and common asteroids.

CCS expressions finite state processes, and three problems of equivalence

Abstract: We examine the computational complexity of testing finite state processes for equivalence in Milner's Calculus of Communicating Systems (CCS). The equivalence problems in CCS are presented as refinements of the familiar problem of testing whether two nondeterministic finite automata (NFA) are equivalent, i.e., accept the same language. Three notions of equivalence proposed for CCS are investigated, namely, observational equivalence, strong observational equivalence, and failure equivalence. We show that observational equivalence can be tested in polynomial time. As defined in CCS, observational equivalence is the limit of a sequence of successively finer equivalence relations, ≈k, where ≈1 is nondeterministic finite automaton equivalence. We prove that, for each fixed k, deciding ≈k is PSPACE-complete. We show that strong observational equivalence can be decided in polynomial time by reducing it to generalized partitioning, a new combinatorial problem of independent interest. Finally, we demonstrate that testing for failure equivalence is PSPACE-complete, even for a very restricted type of process.

Value-function approximations for partially observable Markov decision processes

Abstract: Partially observable Markov decision processes (POMDPs) provide an elegant mathematical framework for modeling complex decision and planning problems in stochastic domains in which states of the system are observable only indirectly, via a set of imperfect or noisy observations. The modeling advantage of POMDPs, however, comes at a price -- exact methods for solving them are computationally very expensive and thus applicable in practice only to very simple problems. We focus on efficient approximation (heuristic) methods that attempt to alleviate the computational problem and trade off accuracy for speed. We have two objectives here. First, we survey various approximation methods, analyze their properties and relations and provide some new insights into their differences. Second, we present a number of new approximation methods and novel refinements of existing techniques. The theoretical results are supported by experiments on a problem from the agent navigation domain.