Assessing and Controlling the Availability of Failure-Degraded Service Agents

Institute for Joint Warfare Analysishttp://archive.org/details/assessingcontr25gaveNAN

Gaussian approximations to service problems : a communication system example

Messages arrive at a group of service channels in accordance with a time-dependent Poisson process. An arrival either (1) immediately begins k-stage Markovian service if an empty channel is reached, or (2) balks and enters a retrial population if the channel sought is busy. Diffusion approximations to the number of messages in service (each stage) and in the retrial population are derived by writing stochastic differential (I+0) equations. Steady-state distributions are found and compared with certain simulation resultssupported in part by the National Science Foundation, Grant AG46 7, at the Naval Postgraduate School, and the Air Force Office of Scientific Research, Grant AFOSR74-2642, at Carnegie Mellon University.http://archive.org/details/gaussianapproxim00gaveN

Modeling and statistical analysis of Medaka bioassay data

Final ReportU.S. Army Medical Research and Development CommandMIMR No. 91MM159862720A3E162720A835.00.009WUDA 33595

Data analysis and modeling of Arctic sea ice subsurface roughness

Statistical data analysis and models are used to characterize and summarize the roughness of the underside of sea ice in the Arctic. Keel spacings and depths are modeled by sculptured exponentials, and by gamma distributions. The data studied was obtained by upward looking sonar on the submarine GURNARD during April, 1976, in the Beaufort Sea. The models and methods should be more widely applicablesupported in part by the Naval Postgraduate School Foundation Research Program and by the Office of Naval Research, Arlington, VA.http://archive.org/details/dataanalysismode00gaveN0001482WR20043N

The Future Theater-Level Model: A Research Project Update

Proceedings of the 1994 Winter Simulation Conference ed. J. D. Tew, S. Manivannan, D. A. Sadowski, and A. F. SeilaResearch has been conducted at the Naval Postgraduate School into new methodologies for joint theater-level combat simulation modeling, emphasizing C3I, operational intelligence, decisionmaking under uncertainty, and aggregated stochastic process modeling. Research outcomes to date as well as a prototype software tool are described in this paper

Modeling and analysis of uncertain time-critical tasking problems

Naval Research Logistics, 53 , No. 6, (Sept. 2006), 588-599.This paper describes modeling and operational analysis of a generic asymmetric services-system situation in which (a) Red agents, potentially threatening, but in another but important interpretation, are isolated friendlies, such as downed pilots, that require assistance and "arrive" according to some partially known and potentially changing pattern in time and space: and (b) Reds have effectively limited unknown deadlines or times of availability for Blue service, i.e., detection, classification, and attack in a military setting or emergency assistance in others. We discuss various service options by Blue service agents and devise several approximations allowing one to compute efficiently those proportions of tasks of different classes that are successfully serviced, or more generally, if different rewards are associated with different classes of tasks, the percentage of the possible reward gained. We suggest heuristic policies of a Blue server to select the next task to perform and to decide how much time to allocate to that service. We discuss this for a number of specific examples

A Continuum of Testing (presentation)

Prepared for the National Test & Evaluation Conference, March 200

Ratchet recruitment in the acute respiratory distress syndrome: lessons from the newborn cry

Patients with acute respiratory distress syndrome (ARDS) have few treatment options other than supportive mechanical ventilation. The mortality associated with ARDS remains unacceptably high, and mechanical ventilation itself has the potential to increase mortality further by unintended ventilator-induced lung injury (VILI). Thus, there is motivation to improve management of ventilation in patients with ARDS. The immediate goal of mechanical ventilation in ARDS should be to prevent atelectrauma resulting from repetitive alveolar collapse and reopening. However, a long-term goal should be to re-open collapsed and edematous regions of the lung and reduce regions of high mechanical stress that lead to regional volutrauma. In this paper, we consider the proposed strategy used by the full-term newborn to open the fluid-filled lung during the initial breaths of life, by ratcheting tissues opened over a series of initial breaths with brief expirations. The newborn’s cry after birth shares key similarities with the Airway Pressure Release Ventilation (APRV) modality, in which the expiratory duration is sufficiently short to minimize end-expiratory derecruitment. Using a simple computational model of the injured lung, we demonstrate that APRV can slowly open even the most recalcitrant alveoli with extended periods of high inspiratory pressure, while reducing alveolar re-collapse with brief expirations. These processes together comprise a ratchet mechanism by which the lung is progressively recruited, similar to the manner in which the newborn lung is aerated during a series of cries, albeit over longer time scales