Experimental study of generalized self-filtering unstable resonators in an ablative-wall flash-lamp-pumped dye laser

The performance of a generalized self-filtering unstable resonator (GSFUR) that consists of two curved mirrors in a nonconfocal scheme with a low magnification of M = -1.62 in an ablative-wall flash-lamp dye laser is reported. The objective was to study the near- and far-field intensity distribution and the divergence of the laser beam. It was found that the output beam has a nearly Gaussian distribution with a pulse duration of ~400 ns FWHM, almost independent of the diameter of the field-limiting aperture, but increases slightly with the pumping rate. A diffraction-limited laser beam of 1.1 mrad was obtained from this laser cavity. The output energy was ~1 mJ when an intracavity glass plate was used as an output coupler. The required relations needed for the GSFUR design were also derived.     

Differential effects of cyclo-oxygenase and thromboxane synthetase inhibition on ventilation-perfusion relationships in acid aspiration-induced acute lung injury

Cyclo-oxygenase metabolites are important regulators of pulmonary vascular and airway tone and may act to regulate ventilation-perfusion (VA/Q) relationships. Hypoxemia that follows aspiration of gastric acid is associated with increased venous admixture, and plasma levels of thromboxane (TX) B2 and 6-keto-PGF2 alpha are increased after experimental acid-induced acute lung injury. The present study was designed to determine the effects of cyclo-oxygenase metabolites on VA/Q relationships in canine acid aspiration. Eighteen anesthetized dogs received 0.2 mL/kg 0.1 N HCl intratracheally; six were pretreated with ibuprofen (IBU), a cyclo-oxygenase inhibitor, 12.5 mg/kg IV, and six other dogs received OKY-046 (OKY), a TX synthetase inhibitor, 0.5 mg/kg IV. The remaining six animals (ACID) served as controls. Continuous distributions of ventilation and perfusion were evaluated with the multiple inert gas elimination technique. Within 30 minutes, acid injury resulted in significant (p < 0.05) decreases in PaO2 from baseline values by 44.7 +/- 5.4 and 47.6 +/- 4.8 mm Hg in the ACID and OKY groups, respectively. Although decreased, the change in PaO2 of 21.0 +/- 4.8 mm Hg in IBU animals was significantly (p < 0.05) attenuated in comparison with the other groups. Ibuprofen increased pulmonary vascular resistance, attenuated perfusion to shunt and low VA/Q areas, and reduced ventilation to unperfused areas for the first 2 hours after acid injury (all p < 0.05), whereas OKY exacerbated hypoxemia and VA/Q inequality.(ABSTRACT TRUNCATED AT 250 WORDS)     

The M/M/c/N queue with balking and reneging

In this paper, a truncated multi-channel queue with reneging and general balk function is considered. The steady-state distribution of the number of units in the system is derived. The expected number of units in both the system and the queue are also obtained. Some previously published results are shown to be special cases of the present results.     

Investigating Autonomic Runtime Management Strategies for SAMR Applications

Dynamic structured adaptive mesh refinement (SAMR) techniques along with the emergence of the computational Grid offer the potential for realistic scientific and engineering simulations of complex physical phenomena. However, the inherent dynamic nature of SAMR applications coupled with the heterogeneity and dynamism of the underlying Grid environment present significant research challenges. This paper presents application/system sensitive reactive and proactive partitioning strategies that form a part of the GridARM autonomic runtime management framework. An evaluation using different SAMR kernels and system workloads is presented to demonstrate the improvement in overall application performance.     

Architectural support for designing fault-tolerant open distributedsystems

An overview of the main techniques for designing fault-tolerant software and hardware systems is provided. The important features of the building blocks (computers, memories, buses, etc.) that can support an efficient implementation of fault-tolerant open distributed systems (FTODSs) are identified. Taking into account the features of these building blocks, an organization for FTODS is proposed. A distributed voting algorithm and a two-level hierarchy for permanent memory are key elements in this scheme. The algorithms needed for transferring files and synchronizing the concurrent activities of the computing modules and for recovery-are ISO standard protocols. Low-level voting and recovery algorithms that can run as a layer of software above the operating system make the open distributed system an attractive environment for applying fault-tolerant techniques     

Prediction of Zeolite-Cemented Sand Tensile Strength by GMDH type Neural Network

Soil tensile strength (q_t) plays an important role in controlling cracks and tensile failures particularly in the design of foundations that usually fail under tensile stresses at the bottom of the treated layer. Soil-cement mixtures are used in many engineering applications including building of stabilized pavement bases and canal lining. Splitting tensile test (STT) is one of the common applied methods for indirect determination of q_t. Given that the determination of q_t of artificially cemented soils from STT—especially for samples with long curing time—is relatively costly and time-consuming, there is a need to develop some empirical models that can estimate determinable properties simply. In the current study, it has been analyzed that whether the Group Method of Data Handling (GMDH)-type Neural Network (NN) is suitable to predict the q_t of sands stabilized with zeolite and cement. For this purpose, a program of STT considering three distinct porosity ratios, four cement contents and six different percent of cement replacement by zeolite in 42, 56 and 90 days of curing time is performed in present study. Active particle (AP) has been introduced as a new parameter for modeling the GMDH-type NN. The performances of the proposed models reveal that GMDH is a reliable and accurate approach to predict the q_t of sands stabilized by zeolite-cement mixture. Proposing an equation in current study, it can be interpreted that AP is one of the key parameters to predict the q_t of zeolite-cemented sands. The sensitivity analysis on the proposed GMDH model with the best performance has shown that the proposed q_t is considerably influenced by cement content variations.     

Polymerizable oil‐in‐oil emulsions: poly(vinyl pyrrolidone) dispersions in reactive PDMS medium

The system N‐vinyl‐2‐pyrrolidone (VP)/polydimethylsiloxane diglycidylether (PDMS‐DGE) is a typical example of an oil‐in‐oil emulsion formed by two non‐miscible liquids, where both phases are polymerizable in a ‘one‐pot’ procedure by two distinct reaction mechanisms. These oil‐in‐oil emulsions were characterized by their stability and by the particle size of the dispersed VP phase. Non‐aqueous dispersions (NADs) are obtained in a first step by free radical polymerization of the dispersed VP phase. The reaction kinetics, studied as a function of the initiator type and concentration, show that the polymerization rate is mainly influenced by the partition coefficient of the initiator between both phases. The NAD particle size could be tailored from a micrometer to a nanometer range by in situ formation of PVP‐PDMS graft copolymer. Hydrophilic–hydrophobic two‐phase materials can be obtained by polycondensation, in the presence of polyamines, of the epoxy‐functionalized PDMS continuous NAD phase. Copyright © 2007 Society of Chemical Industry     

Impact analysis of faults and attacks in large-scale networks

Monitoring and quantifying component behavior is key to, making networks reliable and robust. The agent-based architecture presented here continuously monitors network vulnerability metrics providing new ways to measure the impact of faults and attacks.