Scheduling and data redistribution strategies on star platforms

In this work we are interested in the problem of scheduling and redistributing data on master-slave platforms. We consider the case were the workers possess initial loads, some of which having to be redistributed in order to balance their completion times. We examine two different scenarios. The first model assumes that the data consists of independent and identical tasks. We prove the NP-completeness in the strong sense for the general case, and we present two optimal algorithms for special platform types. Furthermore we propose three heuristics for the general case. Simulations consolidate the theoretical results. The second data model is based on Divisible Load Theory. This problem can be solved in polynomial time by a combination of linear programming and simple analytical manipulations.Dans ce travail on s’intéresse au problème d’ordonnancement et de redistribution de données sur plates-formes maître-esclaves. On considère le cas où les esclaves possèdent des données initiales, dont quelques-unes doivent être redistribuées pour équilibrer leur dates de fin.On examine deux scénarios différents. Le premier modèle suppose que les données sont des tâches indépendantes identiques. On prouve la NP-complétude dans le sens fort pour le cas général, et on présente deux algorithmes pour des plates-formes spéciales.De plus on propose trois heuristiques pour le cas général. Des résultats expérimentaux obtenus par simulation viennent à l’appui des résultats théoriques

Patient-oriented Randomisation - a new clinical trial design

In this thesis a new randomisation designs for clinical trials, called patient-oriented randomisation design, is introduced. This design was developed to counter problems of classical' randomised controlled trials comparing strategies (consisting of different treatments in each strategy) in presence of heterogeneity in patient-drug-interactions. The discrepancies between daily clinical perception and results of randomised controlled trials lead to the conviction that the methodological approach of classical' randomised controlled trials, such as the block randomisation design, is appropriate in this set-up. The patient-oriented approach of the CUtLASS' design reflects everyday clinical practice, by allowing for a patient-oriented choice of one treatment of each strategy. The allocation for a strategy is random. However, the results are highly dependent on the physicians' preferences. The goal of the design described here is to take an intermediate path between randomised controlled trials and the CUtLASS' design. The idea of the new trial design is to randomise two treatment pairs each consisting of one treatment of the one strategy and one treatment of the other strategy in a first step and subsequently, to involve the investigators in deciding for a pair most appropriate to the patients' needs and then to randomise the allocation to one treatment of that chosen pair. After a short introduction, in Chapter 2 basic definitions and notations are given. The considerations concentrate on the properties of the patient-oriented randomisation design which depend mainly on the number of treatments of each strategy. An advantage of the patient-oriented randomisation design (compared to classical randomisation designs) is that in some cases a clear patient-oriented treatment decision of the physician can be seen and investigated. The patient-oriented decision in the CUtLASS' and the patient-oriented randomisation design can lead to unbalanced treatment sample size in each strategy. Chapter 3 investigates the changes of the allocation probability of each treatment and determines the minimum and the maximum allocation probability in both designs. The investigation shows that the interval of possible values of allocation probabilities is lager in the CUtLASS' design. However, the patient-oriented randomisation design ensures that each treatment is in fact administered in the study. Hence, it is possible to compute the number of patients needed to avoid poorly represented treatments and poorly powered comparisons. After this, the practical implementation of the patient-oriented randomisation design are looked at and methods to estimate the probability of imbalance are presented. The block length of the patient-oriented randomisation design is large, hence, modification for the creation for the random list are possible and effective to reduce the probability of imbalance. Finally, Chapter 5 deals with a statistical model to compare two strategies consisting of different treatments. Basic definitions and notations are given for unbalanced one-way classification with fixed effects and the concept of contrasts. Additionally, the required sample size calculation is presented. The power of the associated contrast test depends particularly on the allocation of sample size in each treatment and the expected effect between both strategies. The final consideration shows that heterogeneity of patient-drug-interaction lead to no effect in the Block' design. Randomisation designs such as the CUtLASS' design and the patient-oriented randomisation design only work as well as the physicians selecting the treatments. In a patient-oriented randomisation design, it can be distinguished between patients receiving the treatment not only due to randomisation but due to a patient-oriented decision of the physician (patient-oriented treated patients) and patients receiving the treatment due to randomisation's reasons (randomised choice treated patients). Therefore, the patient-oriented randomisation design allows to test the difference in treatment means between patient-oriented treated patients and randomised choice treated patients in each treatment, each strategy, or overall. In particular, the possibility to analyse the difference between strategies for subgroups consisting of only randomised choice treated patients or only patient-oriented choice treated patients help to test the assumptions about the heterogeneity of patient-drug-interaction in the patient-oriented randomisation design. In the CUtLASS' design, it is not possible to answer this important question. The conclusion consists of a discussion of the results as well as important findings. An outlook on possible future work is also presented

Complexity in electro-optic delay dynamics: modelling, design and applications

International audienceNonlinear delay dynamics have found during the last 30 years a particularly prolific exploration area in the field of photonic systems. Besides the popular external cavity laser diode set-ups, we focus in this article on another experimental realization involving electro-optic (EO) feedback loops, with delay. This approach has strongly evolved with the important technological progress made on broadband photonic and optoelectronic devices dedicated to high-speed optical telecommunications. The complex dynamical systems performed by nonlinear delayed EO feedback loop architectures were designed and explored within a huge range of operating parameters. Thanks to the availability of high-performance photonic devices, these EO delay dynamics led also to many successful, efficient and diverse applications, beyond the many fundamental questions raised from the observation of experimental behaviours. Their chaotic motion allowed for a physical layer encryption method to secure optical data, with a demonstrated capability to operate at the typical speed of modern optical telecommunications. Microwave limit cycles generated in similar EO delay oscillators showed significantly improved spectral purity thanks to the use of a very long fibre delay line. Last but not least, a novel brain inspired computational principle has been recently implemented physically in photonics for the first time, again on the basis of an EO delay dynamical system. In this latter emerging application, the computed result is obtained by a proper 'read-out' of the complex nonlinear transients emerging from a fixed point, the transient being issued by the injection of the information signal to be processed

Global dimming : a regional perspective

In spite of increasing surface temperatures, a falling trend in surface insolation has been observed over the past 50 years at stations worldwide, and a link to anthropogenic aerosols has been suggested. In the present thesis, reports on this "global dimming" are studied and briefly compared to other climate changes such as global warming and atmospheric circulation changes. To get a better understanding of the connection between global dimming and changes in cloud cover, monthly records of surface insolation and cloud amount of varying lengths are investigated for six stations in north-western Europe. The results indicate that global dimming has been present in north-western Europe up to the late 1980s/early 1990s, after which the dimming has turned to a brightening. Although the representativity of merely six stations to the tendency of entire north-western Europe may be debatable, the results correspond well to observed changes in the regional pollution level: There was heavy industrial build-up (particularly in eastern Europe) up to the late 1980s, after which the collapse of the East Bloc and political interventions to limit pollution lead to re-improved air quality. Additionally, some stations experienced an increase in cloud amounts prior to about 1990, succeeded by a decreasing trend, which will have contributed to the observed variations in global radiation. The correlation between surface insolation and cloud cover was found to be high and significant at all stations, and did at two of the stations seem to be the dominating cause of the radiation trend. %At one station, the variations in insolation seemed primarily to be governed by aerosol loads, while at the remaining three stations, the cause was probably a combination of the effects of clouds and aerosols. It appears that in some cases, the effect of aerosol loads and cloud cover collaborate, while in other cases they compete. As the present study shows, dimming may occur in spite of improved aerosol levels, and brightening may occur in spite of increasing cloud covers. The fact that the surface insolation trend is equally dependent on natural variations in clouds as on human-induced variations in aerosol loads, is an important point as debates on global dimming in general tend to be focused on the effect of anthropogenic pollution

Controller design for a universal power input bi-directional battery charger for plug-in electric and hybrid electric vehicles

Questa tesi presenta la progettazione di un carica batterie ideato per operare con un ingresso universale. Il convertitore AC/DC è implementato usando una tipica struttura a due stadi Il controllo di questo dispositivo è implementato usando un controllore PID multi-loop per il raddrizzatore PFC, tramite il controllo average mode della corrente. Un semplice controllore PID è implementato nel convertitore DC/DC ed entrambi utilizzano uno switching PWM. Viene inoltre presentato un nuovo approccio digitale per eliminare il controllore feed-forward dallo schema convenzionale, che semplifica ulteriormente la strategia di controllo. Il controllore digitale del sistema di potenza usa una strategia di switching binaria per i transistor. Essi switchano in base al segno dell’errore, usato come segnale di controllo. Una valutazione comprensiva del convertitore è condotta per analizzare le performance e la robustezza del controllore in termini di stabilità. Alcune condizioni di funzionamento instabili vengono individuate per migliorare il progett

Radiation of photons and gluons in a hot and dense QCD medium

Mis estudios de doctorado se extiende sobre diferentes aspectos teóricos y fenomenológicos de la Cromodinámica Cuántica (QCD) a altas energías y densidades partónicas así como sus conexiones con la fenomenología de las colisiones relativistas núcleo-núcleo (AA) y protón-núcleo (pA) y los experimentos de dispersión inelástica profunda con nucleones y núcleos

Formation and properties of a discrete family of dissipative solitons in a nonlinear optical system

In dieser Arbeit werden dissipative räumliche Solitonen mit experimentellen und theoretischen Methoden untersucht. Die Strukturen werden als lokalisierte Polarisationszustände in der transversalen Feldverteilung eines Laserstrahls beobachtet, der ein optisch nichtlineares System durchläuft. Im Gegensatz zu bisherigen experimentellen Beobachtungen dissipativer Solitonen wird eine Sequenz von Solitonen höherer Ordnung beobachtet, die sich in ihrer inneren Struktur unterscheiden. Ein Schwerpunkt der Arbeit liegt in der Identifikation und Charakterisierung der Mechanismen, die zur Bildung der Solitonen beitragen. Es zeigt sich, dass die Stabilitätseigenschaften der Solitonen eng mit der Dynamik von Schaltfronten verknüpft sind, die zwei stabile räumlich ausgedehnte Zustände des Systems verbinden. Der Existenzbereich der einzelnen Strukturen wird hinsichtlich der wichtigsten Parameter experimentell und numerisch untersucht. In this work, spatial dissipative solitons are analyzed by means of experimental and theoretical methods. The structures are observed as localized polarization states in the transverse field distribution of a laser beam which passes through an optically nonlinear system. In contrast to previous experimental observations of dissipative solitons, a sequence of higher-order solitons which differ in their inner structure is observed. A main part of this work is devoted to the identification and characterization of the mechanisms that lead to the formation of stable solitons. It turns out that the stability properties of the solitons are closely linked with the dynamics of switching fronts that connect two stable spatially extended states of the system. The region of existence of the individual solitons is experimentally and numerically determined with respect to the most important parameters

Elastic Photoproduction of J/psi Vector Mesons at high Photon-Proton Centre-of-Mass Energy at the H1 Experiment at HERA

The elastic photoproduction of J/psi vector mesons at large values of the photon-proton centre-of-mass energy 135GeV<W_{gamma p}<305GeV is studied. The elastic photoproduction cross section sigma(W_{gamma p}) is measured as a function of W_{gamma p}. The differential cross section dsigma/dt is determined in the range |t|<=1.2GeV^2/c^2. This analysis extends the measurements of sigma(W_{gamma p}) and dsigma/dt using H1 data up to highest W_{gamma p} near the kinematic limit given by the parameters of the accelerator of approx. 318GeV. Data for two different event topologies were collected with the H1 detector at the ep-collider HERA during the years 1999 and 2000 resulting in an integrated luminosity of 30.26pb^-1 and 26.90pb^-1 for the analysed data. The level 2 neural network trigger and the backward silicon tracker are important components of the H1 experiment which make this analysis possible. From the W_{gamma p} dependence of the elastic cross section sigma(W_{gamma p})~W_{gamma p}^delta the parameter delta is extracted to be delta=1.17+-0.11+-0.16 for the high W_{gamma p} results of this analysis alone and delta=0.76+-0.03+-0.04 including data of the complete kinematic range of the H1 experiment. The exponential slope b of the differential cross section dsigma/dt~e^{-b|t|} is determined in the high W_{gamma p} regime: b(=180.6GeV)=(5.1+-0.3+-0.2)GeV^-2c^-2, b(=250.7GeV)=(5.4+-0.4+-0.2)GeV^-2c^-2. The intercept alpha_0 and slope alpha' of an effective pomeron trajectory are determined. The W_{gamma p} dependence of the b-slope gives alpha'_b=(0.17+-0.04+-0.01)GeV^-2c^-2. The W_{gamma p} dependence of the differential cross section dsigma/dt yields both parameters: alpha_0=1.21+-0.01+-0.01 and alpha'=(0.14+-0.03+-0.03)GeV^-2c^-2. The two determined slope parameters alpha'_b and alpha' are compatible within errors. Different theoretical approaches are compared to the data. The single pomeron model based on Regge theory does not describe the strong rise of sigma(W_{gamma p}) as a function of W_{gamma p}. The two pomeron model is able to describe the W_{gamma p} dependence of the cross section sigma(W_{gamma p}) within the kinematic regime of HERA, but is not able to describe the combined results of HERA and of fixed target experiments at low values of W_{gamma p}. QCD predictions using different parameterisations of the gluon distribution in the proton are also compared to the measured cross section sigma(W_{gamma p}). The predictions show a strong dependence on the gluon distribution, since the gluon distribution enters the cross section quadratically. The comparison to the measured cross section sigma(W_{gamma p}) is therefore a sensitive test for the gluon distributions, which are determined in an indirect way from inclusive measurements. While some of these analyses result in gluon distributions consistent with the J/psi measurements presented here, others can definitely be excluded

Transport simulations in nanosystems and low-dimensional systems

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