reuse strategies in distributed complex event detection

Software Engineering Society of Korean; Institute for Information Scientists and Engineers; IEEE Reliability Society; KAIST (Korea Advanced Institute of Science and Technology); Korea Information Promotion Agency; Samsung SDS

Low-threshold conjugated polymer distributed feedback lasers on InP substrate

We demonstrate a low threshold polymer solid state thin-film distributed feedback (DFB) laser on an InP substrate with the DFB structure. The used gain medium is conjugated polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) doped polystyrene (PS) and formed by drop-coating method. The second order Bragg scattering region on the InP substrate gave rise to strong feedback, thus a lasing emission at 638.9nm with a line width of 1.2nm is realized when pumped by a 532nm frequency-doubled Nd: YAG pulsed laser. The devices show a laser threshold as low as 7 nJ/pulse.

Dynamic light-scattering characterization of the molecular weight distribution of a broadly distributed phenolphthalein poly(aryl ether ketone)

Using a recently developed laser light-scattering (LLS) procedure, we accomplished the characterization of a broadly distributed unfractionated phenolphthalein poly(aryl ether ketone) (PEK-C) in CHCl3 at 25 degrees C. The laplace inversion of precisely measured intensity-intensity time correlation function from dynamic LLS leads us first to an estimate of the characteristic line-width distribution G(Gamma) and then to the translational diffusion coefficient distribution G(D). By using a previously established calibration of D (cm(2)/s) = 2.37 X 10(-4)M(-0.57), were able to convert G(D) into a differential weight distribution f(w)(M). The weight-average molecular weight M(w) calculated from f(w)(M) agrees well with that directly measured in static LLS. Our results indicate that both the calibration and LLS procedure used in this study are ready to be applied as a routine method for the characterization of the molecular weight distribution of PEK-C. (C) 1996 John Wiley & Sons, Inc.

Variation of active constituents of an important Tibet folk medicine Swertia mussotii Franch. (Gentianaceae) between artificially cultivated and naturally distributed

Concentrations of seven phytochemical constituents (swertiamarin, mangiferin, swertisin, oleanolic acid, 1,5,8-trihydroxy-3methoxyxanthone, 1,8-dihydroxy-3,7-dimethoxyxanthone and 1,8-dihydroxy-3,5-dimethoxyxanthone) of "ZangYinChen" (Swertia mussotii, a herb used in Tibetan folk medicine) were determined and compared in plants collected from naturally distributed high-altitude populations and counterparts that had been artificially cultivated at low altitudes. Levels of mangiferin, the most abundant active compound in this herb, were significantly lower in cultivated samples and showed a negative correlation with altitude. The other constituents were neither positively nor negatively correlated with cultivation at low altitude. Concentrations of all of the constituents varied substantially with growth stage and were highest at the bud stage in the cultivars, but there were no distinct differences between flowering and fruiting stages in this respect. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

MIT SchMUSE: Class-Based Remote Delegation in a Capricious Distributed Environment

MIT SchMUSE (pronounced "shmooz") is a concurrent, distributed, delegation-based object-oriented interactive environment with persistent storage. It is designed to run in a "capricious" network environment, where servers can migrate from site to site and can regularly become unavailable. Our design introduces a new form of unique identifiers called "globally unique tickets" that provide globally unique time/space stamps for objects and classes without being location specific. Object location is achieved by a distributed hierarchical lazy lookup mechanism that we call "realm resolution." We also introduce a novel mechanism called "message deferral" for enhanced reliability in the face of remote delegation. We conclude with a comparison to related work and a projection of future work on MIT SchMUSE.

Near-Optimal Distributed Failure Circumscription

Small failures should only disrupt a small part of a network. One way to do this is by marking the surrounding area as untrustworthy --- circumscribing the failure. This can be done with a distributed algorithm using hierarchical clustering and neighbor relations, and the resulting circumscription is near-optimal for convex failures.

Vegetation and Topographic Control of Wind-blown Snow Distributions in Distributed and Aggregated Simulations for an Arctic Tundra Basin

Essery, RLH & JW, Pomeroy, (2004). Vegetation and topographic control of wind-blown snow distributions in distributed and aggregated simulations. Journal of Hydrometeorology, 5, 735-744.

The evaluation of evidence for exponentially distributed data

C.G.G. Aitken, Q. Shen, R. Jensen and B. Hayes. The evaluation of evidence for exponentially distributed data. Computational Statistics & Data Analysis, vol. 51, no. 12, pp. 5682-5693, 2007.

A Guide to Distributed Digital Preservation

This volume is devoted to the broad topic of distributed digital preservation, a still-emerging field of practice for the cultural memory arena. Replication and distribution hold out the promise of indefinite preservation of materials without degradation, but establishing effective organizational and technical processes to enable this form of digital preservation is daunting. Institutions need practical examples of how this task can be accomplished in manageable, low-cost ways."--P. [4] of cover

Asynchronous Auction for Distributed Nonlinear Resource Allocation Problem

Resource Allocation Problems (RAPs) are concerned with the optimal allocation of resources to tasks. Problems in fields such as search theory, statistics, finance, economics, logistics, sensor & wireless networks fit this formulation. In literature, several centralized/synchronous algorithms have been proposed including recently proposed auction algorithm, RAP Auction. Here we present asynchronous implementation of RAP Auction for distributed RAPs.

Priority-Based Synchronization of Distributed Data

We consider the general problem of synchronizing the data on two devices using a minimum amount of communication, a core infrastructural requirement for a large variety of distributed systems. Our approach considers the interactive synchronization of prioritized data, where, for example, certain information is more time-sensitive than other information. We propose and analyze a new scheme for efficient priority-based synchronization, which promises benefits over conventional synchronization.

Mermera: Non-Coherent Distributed Shared Memory for Parallel Computing

The proliferation of inexpensive workstations and networks has prompted several researchers to use such distributed systems for parallel computing. Attempts have been made to offer a shared-memory programming model on such distributed memory computers. Most systems provide a shared-memory that is coherent in that all processes that use it agree on the order of all memory events. This dissertation explores the possibility of a significant improvement in the performance of some applications when they use non-coherent memory. First, a new formal model to describe existing non-coherent memories is developed. I use this model to prove that certain problems can be solved using asynchronous iterative algorithms on shared-memory in which the coherence constraints are substantially relaxed. In the course of the development of the model I discovered a new type of non-coherent behavior called Local Consistency. Second, a programming model, Mermera, is proposed. It provides programmers with a choice of hierarchically related non-coherent behaviors along with one coherent behavior. Thus, one can trade-off the ease of programming with coherent memory for improved performance with non-coherent memory. As an example, I present a program to solve a linear system of equations using an asynchronous iterative algorithm. This program uses all the behaviors offered by Mermera. Third, I describe the implementation of Mermera on a BBN Butterfly TC2000 and on a network of workstations. The performance of a version of the equation solving program that uses all the behaviors of Mermera is compared with that of a version that uses coherent behavior only. For a system of 1000 equations the former exhibits at least a 5-fold improvement in convergence time over the latter. The version using coherent behavior only does not benefit from employing more than one workstation to solve the problem while the program using non-coherent behavior continues to achieve improved performance as the number of workstations is increased from 1 to 6. This measurement corroborates our belief that non-coherent shared memory can be a performance boon for some applications.

AIDA-Based Distributed File System

This paper describes a prototype implementation of a Distributed File System (DFS) based on the Adaptive Information Dispersal Algorithm (AIDA). Using AIDA, a file block is encoded and dispersed into smaller blocks stored on a number of DFS nodes distributed over a network. The implementation devises file creation, read, and write operations. In particular, when reading a file, the DFS accepts an optional timing constraint, which it uses to determine the level of redundancy needed for the read operation. The tighter the timing constraint, the more nodes in the DFS are queried for encoded blocks. Write operations update all blocks in all DFS nodes--with future implementations possibly including the use of read and write quorums. This work was conducted under the supervision of Professor Azer Bestavros (best@cs.bu.edu) in the Computer Science Department as part of Mohammad Makarechian's Master's project.

dPAM: A Distributed Prefetching Protocol for Scalable Asynchronous Multicast in P2P Systems

We leverage the buffering capabilities of end-systems to achieve scalable, asynchronous delivery of streams in a peer-to-peer environment. Unlike existing cache-and-relay schemes, we propose a distributed prefetching protocol where peers prefetch and store portions of the streaming media ahead of their playout time, thus not only turning themselves to possible sources for other peers but their prefetched data can allow them to overcome the departure of their source-peer. This stands in sharp contrast to existing cache-and-relay schemes where the departure of the source-peer forces its peer children to go the original server, thus disrupting their service and increasing server and network load. Through mathematical analysis and simulations, we show the effectiveness of maintaining such asynchronous multicasts from several source-peers to other children peers, and the efficacy of prefetching in the face of peer departures. We confirm the scalability of our dPAM protocol as it is shown to significantly reduce server load.

Distributed Parallel Computing in Mermera: Mixing Noncoherent Shared Memories

Programmers of parallel processes that communicate through shared globally distributed data structures (DDS) face a difficult choice. Either they must explicitly program DDS management, by partitioning or replicating it over multiple distributed memory modules, or be content with a high latency coherent (sequentially consistent) memory abstraction that hides the DDS' distribution. We present Mermera, a new formalism and system that enable a smooth spectrum of noncoherent shared memory behaviors to coexist between the above two extremes. Our approach allows us to define known noncoherent memories in a new simple way, to identify new memory behaviors, and to characterize generic mixed-behavior computations. The latter are useful for programming using multiple behaviors that complement each others' advantages. On the practical side, we show that the large class of programs that use asynchronous iterative methods (AIM) can run correctly on slow memory, one of the weakest, and hence most efficient and fault-tolerant, noncoherence conditions. An example AIM program to solve linear equations, is developed to illustrate: (1) the need for concurrently mixing memory behaviors, and, (2) the performance gains attainable via noncoherence. Other program classes tolerate weak memory consistency by synchronizing in such a way as to yield executions indistinguishable from coherent ones. AIM computations on noncoherent memory yield noncoherent, yet correct, computations. We report performance data that exemplifies the potential benefits of noncoherence, in terms of raw memory performance, as well as application speed.