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Distributed Manner (distributed + manner)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Specification and detection of performance problems with ASL

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 11 2007
Michael Gerndt
Abstract Performance analysis is an important step in tuning performance-critical applications. It is a cyclic process of measuring and analyzing performance data, driven by the programmer's hypotheses on potential performance problems. Currently this process is controlled manually by the programmer. The goal of the work described in this article is to automate the performance analysis process based on a formal specification of performance properties. One result of the APART project is the APART Specification Language (ASL) for the formal specification of performance properties. Performance bottlenecks can then be identified based on the specification, since bottlenecks are viewed as performance properties with a large negative impact. We also present the overall design and an initial evaluation of the Periscope system which utilizes ASL specifications to automatically search for performance bottlenecks in a distributed manner. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Water resources in mountain regions: a methodological approach to assess the water balance in a highland-lowland-system

HYDROLOGICAL PROCESSES, Issue 5 2007
Rolf Weingartner
Abstract Mountains and highlands are typically areas that provide considerable quantities of water, the latter being an important resource for the lowlands. These run-off quantities remain discernible in the superior-scale river systems and significantly contribute to the global water resources. Therefore, mountain regions ought to be given specific consideration with regard to management endeavours. Although well known in principle, details of water resources originating from mountains remain under discussion. A new approach has been introduced, which depicts the water balance of Switzerland in a spatially distributed manner, based on catchments of about 150 km2. The main feature of this approach is the areal precipitation, which is calculated using run-off, evaporation and storage change of glaciers, instead of being derived from gauged precipitation values. This methodology was selected because measurement and regionalization of precipitation remain subject to large uncertainties in mountainous areas. Subsequently, the view is widened to the European Alps, which, as compared with the surrounding lowlands, contribute considerably higher annual discharge, especially in the summer months. Finally, the focus is put on the hydrological significance of mountains in general. In dry regions, mountains, in particular, are indispensable contributors to the water resources downstream. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Priority-based adaptive routing in NGEO satellite networks

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2007
Ömer Korçak
Abstract In a non-geostationary satellite constellation with inter satellite links (ISLs), there could be many shortest paths between two satellites in terms of hop count. An efficient routing algorithm should effectively use these paths in order to distribute traffic to ISLs in a balanced way and to improve the performance of the system. This paper presents and evaluates a novel priority-based adaptive shortest path routing (PAR) scheme in order to achieve this goal. PAR sets the path towards the destination in a distributed manner, using a priority mechanism depending on the past utilization and buffering information of the ISLs. Moreover, to avoid unnecessary splitting of a flow and to achieve better utilization of ISLs, enhanced PAR (ePAR) scheme is proposed. This paper evaluates performance of the proposed techniques by employing an extensive set of simulations. Furthermore, since there are a number of ePAR parameters that should be adjusted depending on the network and traffic characteristics, a detailed analysis of ePAR scheme is provided to form a framework for setting the parameters. This paper also includes a method for adaptation of the proposed algorithms to minimum-delay path routing. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Virtual reality simulation training can improve technical skills during laparoscopic salpingectomy for ectopic pregnancy

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 12 2006
R Aggarwal
Objectives, To assess the first commercially available virtual reality (VR) simulator to incorporate procedural modules for training of inexperienced gynaecological surgeons to perform laparoscopic salpingectomy for ectopic pregnancy. Design, Prospective cohort study. Setting, Departments of surgery and gynaecology in central London teaching hospitals. Sample, Thirty gynaecological surgeons were recruited to the study, and were divided into novice (<10 laparoscopic procedures), intermediate (20,50) and experienced (>100) groups. Methods, All subjects were orientated to the VR simulator with a basic skills task, followed by performing ten repetitions of the virtual ectopic pregnancy module, in a distributed manner. Main outcome measures, Operative performance was assessed by the time taken to perform surgery, blood loss and total instrument path length. Results, There were significant differences between the groups at the second repetition of the ectopic module for time taken (median 551.1 versus 401.2 versus 249.2 seconds, P= 0.001), total blood loss (median 304.2 versus 187.4 versus 123.3 ml, P= 0.031) and total instrument path length (median 17.8 versus 8.3 versus 6.8 m, P= 0.023). The learning curves of the experienced operators plateaued at the second session, although greater numbers of sessions were necessary for intermediate (seven) and novice (nine) surgeons to achieve similar levels of skill. Conclusions, Gynaecological surgeons with minimal laparoscopic experience can improve their skills during short-phase training on a VR procedural module. In contrast, experienced operators showed nonsignificant improvements. Thus, VR simulation may be useful for the early part of the learning curve for surgeons who wish to learn to perform laparoscopic salpingectomy for ectopic pregnancy. [source]