Customer‐managed end‐to‐end lightpath provisioning

Customer‐owned and managed optical networks bring new cost‐saving benefits. Two types of such networks are becoming widely used: metro dark fiber networks and long‐haul leased wavelength networks. Customers may invoke a special QoS mechanism where end‐to‐end (E2E) lightpaths are dynamically established across multiple independently managed customer domains. The cost of bandwidth is substantially reduced since it largely becomes a capital cost rather than an ongoing service charge. Customers can optimize the overall resource consumption by utilizing resources from different suppliers. Remote peering and transit reduce the Internet connectivity cost. Bandwidth and quality of service are guaranteed because customers directly peer with each other using transport networks. An architecture for a customer‐managed E2E lightpath provisioning system is presented. Integration with Grid applications is discussed and a prototype demonstration is described. Copyright © 2005 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.     

Forward-Looking WDM Network Reconfiguration with Per-Link Congestion Control

We study reconfigurations of wavelength-routed Wavelength Division Multiplexing (WDM) networks in response to lightpath demand changes, with the objective of servicing more lightpath demands without additional network resources from a long-term network operation point of view. For the reconfiguration problem under study, we assume WDM network operators are provided with lightpath demands in batches. With limited network resources, our problem has two unique challenges: balancing network resource allocations between current and future lightpath demands, and modeling future lightpath demands. The first challenge implies making tradeoffs between accepting as many current immediate lightpath demands as possible and reserving a certain amount of network resources for near future predicted lightpath demands. The second challenge implies modeling future predicted lightpath demands, which are not exactly known or certain as the current lightpath demands. Our proposed model allows a natural separation between the operation of the optical layer and the user traffic layer (predominantly the IP-layer), while supporting their interactions, for which we propose a new formulation for per-link congestion control, associated with a mathematical solution procedure. Our simulation results reveal that by properly controlling resource allocations in the current session using our proposed mechanism, rejections in future sessions are greatly reduced.     

Detecting mistakes in engineering models: the effects of experimental design

This paper presents the results of an experiment with human subjects investigating their ability to discover a mistake in a model used for engineering design. For the purpose of this study, a known mistake was intentionally placed into a model that was to be used by engineers in a design process. The treatment condition was the experimental design that the subjects were asked to use to explore the design alternatives available to them. The engineers in the study were asked to improve the performance of the engineering system and were not informed that there was a mistake intentionally placed in the model. Of the subjects who varied only one-factor-at-a-time, fourteen of the twenty-seven independently identified the mistake during debriefing after the design process. A much lower fraction, one out of twenty-seven engineers, independently identified the mistake during debriefing when they used a fractional factorial experimental design. Regression analysis shows that relevant domain knowledge improved the ability of subjects to discover mistakes in models, but experimental design had a larger effect than domain knowledge in this study. Analysis of video tapes provided additional confirmation as the likelihood of subjects to appear surprised by data from a model was significantly different across the treatment conditions. This experiment suggests that the complexity of factor changes during the design process is a major consideration influencing the ability of engineers to critically assess models.     

Les groupes informels dans les organisations: cadre général d'analyse.

Reviews the results of studies of the role of informal groups within organizations. Different conceptions of the nature and characteristics of informal groups are considered. Factors that lead to the formation of informal groups are considered. The internal functions of informal groups and their interactions with the organization as a whole are described. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Atmospheric corrections for improved satellite passive microwave snow cover retrievals over the Tibet Plateau

Since 1978, satellite passive microwave data have been used to derive hemispheric-scale snow cover maps. The seasonal and inter-annual variability of the microwave snow maps compares reasonably well with simultaneous maps of snow cover derived from satellite-based, visible-wavelength sensors. In general, the microwave-derived maps tend to underestimate snow extent during fall and early winter, due to a weak signal from shallow and intermittent snow cover. During the early snow season the microwave may underestimate by as much as 20%, decreasing to a few percent during mid-winter and spring. The Tibet Plateau is the only large geographic region where microwave retrievals tend to consistently overestimate snow-covered area compared to the visible data. This has been noted in limited case studies comparing visible and microwave snow data. The persistence of the microwave overestimate is also demonstrated in multi-year climatologies. Current microwave algorithms used to derive snow cover are based on ground or aircraft measurements that are later fine-tuned to match satellite retrievals. In this way, the algorithms have implicitly accounted for the presence of an atmosphere, because the surface or scene brightness values applied in the algorithms have actually passed through the atmosphere along their path to reach the satellite sensor. These methods are reasonably accurate when applied as a global algorithm to most snow-covered regions. However, a thinner atmosphere between the surface and satellite is likely the source of the consistent snow extent overestimate on the Tibet Plateau, where elevations range from 3200 to 5000 m. Wang and Manning (2003) have suggested that adjustments to ground or aircraft microwave measurements are needed to compare with satellite-based measurements. Based on their work, we propose a methodology to adjust satellite-based microwave brightness temperatures as a function of the observed surface elevation, thereby reducing the microwave snow cover overestimate on the Tibet Plateau. We include comparisons to snow maps derived from selected visible-wavelength products. We estimate that the adjusted microwave algorithm reduces the Tibet Plateau area of disagreement with the visible products by approximately 17% (468,000 km²) over the snow season.     

Elbow arthroscopy in trauma and reconstruction

Grief and bereavement following the death of a loved one present clients with significant challenges to the physical, emotional, and spiritual health and well-being. The grieving process for the person with HIV infection may be compounded by shame, stigma, and lack of social support. For communities with the highest prevalence of HIV infection, AIDS-related losses have resulted in mounting, and often overlapping, bereavements. Addressing the impact of these bereavements on the physical and emotional health of clients and their survivors is imperative to designing appropriate interventions to alleviate the potential adverse health outcomes associated with epidemic loss. Facilitating the grief work of HIV positive persons and their loved ones serves to assuage unhealthy sequelae, promote effective coping skills, and provide opportunities for personal growth.     

Appraisals, coping, and stress in breast cancer screening: A longitudinal investigation of causal structure.

The cognitive-appraisal model of R. S. Lazarus and S. Folkman (1984) is one of the most prominent theories of stress. As integral elements in this model, appraisal and coping have both been proposed as mediators of the stress response. The purpose of this study was to test the predictive power of the theoretical model based on 2 competing formulations using structural equation modeling techniques. One conceptual model proposed that coping influences stress through appraisal; the other proposed that appraisals impact on stress via coping. 506 women (aged 50+ yrs) undergoing breast cancer screening completed measures of appraisal, coping, and stress. Support was found for both hypothesized causal structures. The implications of these findings are discussed in terms of Lazarus's theoretical perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temperature and performance variations along single chamber solid oxide fuel cells

The catalytic activity of single chamber solid oxide fuel cells (SC-SOFCs) with respect to hydrocarbon fuels induces a major overheating of the fuel cell, temperature variations along its length, and changes in the original fuel/air composition mainly over the anode component. This paper assesses the temperature gradients and the variations in performance along electrolyte-supported Ni-YSZ/YSZ/LSM cells fed with methane gas. The investigations are performed in a useful range of CH₄/O₂ ratios between 1.0 and 2.0, in which the furnace temperature and flow rate of methane–air mixtures are held constant at 700 °C and 450 sccm, respectively. Electrochemical impedance spectroscopy (EIS) is used to sense the temperature at the location where smaller size cathodes are positioned on the opposite side of a full-size anode. Due to temperature increases, cells always perform better when the small cathodes are located at the inlet as well as at a CH₄/O₂ ratio of 1.0. With an increase in ratio, the results show the presence of artefacts due to the use of an active LSM material for the combustion of methane, and open-type gas distribution plates for the single chamber reactor.