Fairness in Communication and Computer Network Design

In communication networks, fair sharing of resources is an important issue for one main reason. The growth of network capacity is in general not matching the rapid growth of traffic. Consequently, the resources consumed by each user have to be limited. This implies that users cannot always be assigned the end-to-end bandwidth they ask for. Instead, the limited network resources should be distributed to users in a way that assures fair end-to-end bandwidth assignment among them. Obtaining fairness between network users and at the same time assuring efficient network utilization, is a source of non-trivial network optimization problems. Complicating factors are that each user has limited access to the (limited) network resources and that different users require and consume different amounts and types of resources. In this thesis different types of optimization problems associated with fair resource sharing in communication networks are studied. Initially, the notions of max-min fairness, proportional fairness, alpha-fairness etc., are put in a formal framework of fair rational preference relations. A clear, unified definition of fairness is presented. The theory is first applied to different types of allocation problems. Focus is put on convex and non-convex max-min fair traffic allocation problems, and a difference in difficulty between the two groups of problems is demonstrated. The studies are continued by an investigation of proportionally fair dimensioning. Two different cases are studied -- a simpler, when no resilience to failures is required, and a more complicated, assuming the possibility of link failures. In the context of fair sharing of the resources of a communication network, this thesis presents several original theoretical findings as well as solution algorithms for the studied problems. The results are accompanied by numerical results, illustrating algorithm efficiency for virtually all of the studied problems

PHENIX measurement of jet properties and their modification in heavy-ion collisions

The properties of jets produced in p+p, d+Au and Au+Au collisions at sqrt{s_NN}=200 GeV are studied using the method of two particle correlations. The trigger particle is assumed to be a leading particle from a high p_T jet while the associated particle is assumed to come from either the same jet or the away jet. From the angular width and yield of the same and away side correlation peaks, the parameters characterizing the jet properties are extracted.Comment: 4 pages, 3 figures, contribution to the proceedings of the 17th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter, Oakland, January 11-17, 2004). To appear in the proceedings (Journal of Physics G

Hadron production in the forward and backward rapidities in dAu collisions at RHIC

We have developed new techniques to detect hadrons with the PHENIX muon spectrometers. This allows us to study the centrality dependent nuclear modification factor $R_{CP}$ with high $p_{T}$ hadrons in both forward (d direction) and backward (Au direction) rapidities, $1 < |\eta| < 2$, in dAu collisions at $\sqrt{s_{NN}} = 200 GeV$. Preliminary results show a suppression (enhancement) of high $p_{T}$ hadron production in central $0-20$ dAu collisions relative to the peripheral one ($60-88$ in centrality) at forward (backward) rapidity.Comment: 4 pages, 4 figures, Quark Matter 2004 tal

Neutral Pion Distributions in PHENIX at RHIC

Transverse momentum spectra for identified $\pi^0$'s in the range 1 GeV/c $< p_T <$ 4 GeV/c have been measured by the PHENIX experiment in Au-Au collisions at $\sqrt{s}=130$ GeV. The spectra from peripheral nuclear collisions are consistent with the simple expectation of scaling the spectra from p+p collisions by the average number of nucleon-nucleon binary collisions. The spectra from central collisions and the ratio of central/peripheral spectra are significantly suppressed when compared to point-like scaling.Comment: 6 pages, 3 figure

Two Particle Azimuthal Correlation Measurements in PHENIX

Two particle azimuthal correlation functions are presented for charged hadrons produced in Au-Au collisions at RHIC sqrt(s_NN)=200 GeV.The correlation functions indicate sizeable asymmetries and anisotropies. The trend of the asymmetries is compatible with the presence of emission patterns associated with mini-jets. The magnitude and the trend of the differential anisotropies v_2(p_T) and v_2(N_Part), provide important model constraints.Comment: 4 pages 3 fig

Results on Photon Production in Au+Au Collisions at RHIC

The status of the search for direct photons in Au+Au collisions at sqrt{s_NN} = 130 GeV and sqrt{s_NN} = 200 GeV with the PHENIX experiment is presented. Within errors, no excess of direct photons was found in a first analysis pass done on a limited data set. Significantly reduced systematic and statistical uncertainties are expected in future analyses.Comment: 4 pages, 3 figures. Talk presented at the Quark Matter 2002 conference, Nantes, France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A

Hållbara drivmedel - finns de?

Vårt syfte med denna rapport är att diskutera drivmedel från ett brett perspektiv ur hållbarhetssynpunkt. Biodrivmedel och el analyseras och jämförs med fossila drivmedel. Vår målsättning är att försöka peka ut under vilka förutsättningar som drivmedel kan anses försvarbara ur hållbarhetssynpunkt och vilka system som vi bör utveckla respektive vilka system som vi bör undvika. En övergripande slutsats i studien är att man inte kan fastställa hur hållbara biodrivmedel blir i framtiden utan att samtidigt beakta skala och tillväxttakt. Dagens biodrivmedel i Sverige är hållbara utifrån den aktuella produktionsvolymen och gynnar utvecklingen av nya drivmedelssystem, men man bör ställa hårda krav på energi- och klimateffektivitet i hela bränslekedjan (från odling till tank) vid ökade produktionsvolymer. Det är av hög prioritet att utveckla bränslesnåla bilar och här kommer elhybridteknologin och elbilar att bli allt viktigare. En långsiktig strategi för biodrivmedel bör innehålla satsningar på teknologi både för termisk förgasning och biologiska omvandlingsmetoder för lignocellulosa eftersom detta är kompletterande lika mycket som konkurrerande teknologier samt ger större flexibilitet och mindre risk för konflikter. Biogas från restprodukter har stora miljöfördelar och kan expandera med liten risk för konflikter. Certifiering (rätt utformat) är ett viktigt och nödvändigt verktyg på vägen mot mer hållbara drivmedel och vid ökade produktionsvolymer, men dessa system ska inte överskattas då de aldrig kan innefatta alla hållbarhetskriterier. Socio-ekonomiska aspekter som arbetsförhållanden, lokal landsbygdsutveckling osv samt effekter av ökad markkonkurrens måste i första hand lösas med generella åtgärder som nationell lagstiftning, fördelningspolitik, program och planer som i sin tur bör stödjas av internationella avtal och utvecklingssamarbete på olika nivåer. Oavsett utvecklingen i Sverige eller EU så kommer biodrivmedelsproduktionen globalt att öka, framför allt i utvecklingsländerna. Det är därför viktigt att ta vara på den möjlighet vi har idag att medverka i utvecklingen och införandet av hållbarhetskriterier. Förnybara drivmedel kan, med rätt utformning och styrmedel för lämplig tillväxttakt och produktionsvolym, leda till en positiv och hållbar utveckling i både industri- och utvecklingsländer

Materials for Sustainable Nuclear Energy: A European Strategic Research and Innovation Agenda for All Reactor Generations

Nuclear energy is presently the single major low-carbon electricity source in Europe and is overall expected to maintain (perhaps eventually even increase) its current installed power from now to 2045. Long-term operation (LTO) is a reality in essentially all nuclear European countries, even when planning to phase out. New builds are planned. Moreover, several European countries, including non-nuclear or phasing out ones, have interests in next generation nuclear systems. In this framework, materials and material science play a crucial role towards safer, more efficient, more economical and overall more sustainable nuclear energy. This paper proposes a research agenda that combines modern digital technologies with materials science practices to pursue a change of paradigm that promotes innovation, equally serving the different nuclear energy interests and positions throughout Europe. This paper chooses to overview structural and fuel materials used in current generation reactors, as well as their wider spectrum for next generation reactors, summarising the relevant issues. Next, it describes the materials science approaches that are common to any nuclear materials (including classes that are not addressed here, such as concrete, polymers and functional materials), identifying for each of them a research agenda goal. It is concluded that among these goals are the development of structured materials qualification test-beds and materials acceleration platforms (MAPs) for materials that operate under harsh conditions. Another goal is the development of multi-parameter-based approaches for materials health monitoring based on different non-destructive examination and testing (NDE&T) techniques. Hybrid models that suitably combine physics-based and data-driven approaches for materials behaviour prediction can valuably support these developments, together with the creation and population of a centralised, “smart” database for nuclear materials

Cost-analyzes based on a prospective, randomized study comparing laparoscopic colposuspension with a tension-free vaginal tape procedure.

Background. The aim of this study was to compare laparoscopic colposuspension with tension-free vaginal tape (TVT) in terms of costs to the county. Methods. In a prospective, randomized study, we approached 270 consecutive women presenting for evaluation of stress urinary incontinence symptoms at one university hospital. Preoperatively, and at 1-year follow-up, the women underwent urodynamic evaluation, an ultra-short pad-test and completed a lower urinary tract symptoms questionnaire. We randomized 79 consenting, eligible women to either procedure; a 1-year follow-up examination was performed on 68/71 (96%) women that were available. The procedures were performed as described previously. Main outcome measures were all relevant costs for goods and services associated with the procedures. Results. The baseline characteristics of the two groups were similar. The TVT procedure was performed significantly faster than the laparoscopic colposuspension, i.e. 44.9 ± 14.2 min compared with 60.5 ± 13.4 min (p< 0.0001). Even so, procedural costs were significantly lower for laparoscopic colposuspension than for TVT (euro 1273.4 compared with euro 1342.8 p< 0.001). At the 1-year follow-up visit, three women operated on with TVT and one operated on with laparoscopic colposuspension required re-operation for continuous stress urinary incontinence. One women operated on with TVT had her sling cut for bladder-emptying problems. Total costs, including re-operations were euro 1462.6 for a TVT procedure andeuro 1314.5 for a laparoscopic colposuspension. Conclusion. In our hands, the laparoscopic colposuspension was less expensive to the county than the TVT procedure