45869693
Inter-Departure Times in Base-Stock Inventory-Queues
An inventory-queue is an inventory system controlled by a processing station with queueing. They are natural building blocks for supply chain models. An important and largely open issue for inventory queues is the characterization of their departure processes. In an inventory-queue, departures are triggered either by a job arrival when the output buffer is not empty or otherwise by a service completion. Such departures are more difficult to analyze than departures from a standard queue. The main results in this study are expressions for the probability distributions and squared coefficient of variations of inter-departure times for base-stock inventory-queues with birth–death production processes.
34284992
An Algorithmic Approach for Sensitivity Analysis of Perturbed Quasi-Birth-and-Death Processes
In this paper, we present an algorithmic approach for sensitivity analysis of stationary and transient performance measures of a perturbed continuous-time level-dependent quasi-birth-and-death (QBD) process with infinitely-many levels. By developing a new LU-type RG-factorization using the censoring technique, we obtain the maximal negative inverse of the infinitesimal generator of the QBD process. The derivatives of the stationary performance measures of the QBD process can then be expressed and computed in terms of the maximal negative inverse, overcoming the computational difficulty arising from the use of group inverses of infinite size in the current literature (see Cao and Chen [11]). We also use a stochastic integral functional to study the transient performance measure of the QBD process and show how to use the algorithmic approach for its sensitivity analysis. As an example, a perturbed MAP/PH/1 queue is also analyzed.
9143242
Update Monitoring: The CQ Project
In rapidly growing open environments such as the Internet, users experience information starvation in the midst of data overload, due to difficulties similar to finding the needle in a haystack. Update monitoring is a promising area of research where we bring the right information to the user at the right time, instead of forcing the user through manual browsing or repeated submission of queries. As an example of update monitoring research, we outline our work in the Continual Queries (CQ) project, including its basic concepts, software architecture, and current implementation status.
3564308
Using Domain Ontologies to Help Track Data Provenance
Traditional techniques for tracking data provenance have difficulty adapting to the dynamics of the Web. This paper proposes a scheme for provenance estimation, based on domain ontologies. This scheme is part of the POESIA approach for multi-step integration of semi-structured data. The ontologies used for tracking provenance also help to describe, discover, reuse and integrate data and services. In contrast to traditional techniques, this scheme derives data provenance with fewer annotations at the extensional level and thus lower maintenance costs. Additionally, it promotes the use of ontologies to categorize and correlate scopes of data sets, thereby capturing the operational semantics of data integration processes.
24660543
A note on the lower bounds of signed domination number of a graph
Abstract Let G = (V, E) be a graph. For a function f : V → {−1, 1}, the weight of f is w(f) = Σv ∈ V f(v). For a vertex v in V, we define f[v] = Σu∈N[v] f(u). A signed dominating function of G is a function f : V → {−1, 1} such that f[v] ⩾ 1 for all v ∈ V. The signed domination number γs(G) of G is the minimum weight of a signed dominating function on G. A signed dominating function of a weight γs(G) we call a γs-function of G. In this paper, we study the signed domination problem of general graph, and obtain some lower bounds of the signed domination number of a graph, and show that these lower bounds are sharp, and extend a result in Dunbar et al. (1995).
9137886
Dynamic restructuring of transactional workflow activities: a practical implementation method
We describe a practical method to implement the dynamic restructuring of distributed transactional activities with several main advantages. First, it guarantees the correctness of dynamic restructuring operations as well as that of ongoing transactional activities. Second, it is general enough to accommodate a wide range of work ow activities' dynamic restructuring requirements. Third, it facilitates the deployment of dynamic restructuring operations on production systems. Our method combines adaptors, microprotocols, and incremental specialization, building modularly on the system components (e.g., RTF [1], OCP [28], MARS [4]) that we previously developed to support distributed extended transaction processing [19]. A prototype implementation based on this method is built on top of Transarc Encina, a commercial online transaction processing (OLTP) monitor. To our knowledge, this is the rst implementation of dynamic restructuring on top of commercial OLTP systems.
17663309
Impact of network resource constraints on the performance of wireless sensor relay networks
This work studies the impact of the network resource constraints on the performance of wireless sensor multi-hop relay networks. A differential space-time coding and the cooperative relay scheme for cross layer design is introduced in multi-hop wireless sensor networks. To analyze the network performance of such a system, the relay system from source to destination is simplified as a virtual bit pipe line, and a Markov chain model as well as an M/G/1 queueing system are used. The closed form expression for throughput and delay are derived in the infinite buffer case. A truncated Markov chain model and an M/G/1/K queueing system are used to model the finite buffer situation. Moreover, the system drop probability and the go through delay are studied based on the models.