Recently, erasure networks have received significant attention in the literature as they are used to model both wireless and wireline packet-switched networks. Many packet-switched data networks like wireless mesh networks, the Internet, and Peer-to-peer networks can be modeled as erasure networks. In any erasure network, path diversity works by setting up multiple parallel connections between the end points using the topological path redundancy of the network. Our analysis of diversity over erasure networks studies the problem of rate allocation (RA) across multiple independent paths, coding over erasure channels, and the trade-off between rate and diversity gain in three consecutive chapters. In the chapter 2, Forward Error Correction (FEC) is applied across multiple independent paths to enhance the end-to-end reliability. We prove that the probability of irrecoverable loss (P_E) decays exponentially with the number of paths. Furthermore, the RA problem across independent paths is studied. Our objective is to find the optimal RA, i.e. the allocation which minimizes P_E. Using memoization technique, a heuristic suboptimal algorithm with polynomial runtime is proposed for RA over a finite number of paths. This algorithm converges to the asymptotically optimal RA when the number of paths is large. For practical number of paths, the simulation results demonstrate the close-to-optimal performance of the proposed algorithm. Chapter 3 addresses the problem of lower-bounding the probability of error (PE) for any block code over an input-independent channel. We derive a lower-bound on PE for a general input-independent channel and find the necessary and sufficient condition to meet this bound with equality. The rest of this chapter applies this lower-bound to three special input-independent channels: erasure channel, super-symmetric Discrete Memoryless Channel (DMC), and q-ary symmetric DMC. It is proved that Maximum Distance Separable (MDS) codes achieve the minimum probability of error over any erasure channel (with or without memory). Chapter 4 addresses a fundamental trade-off between rate and diversity gain of an end-to-end connection in erasure networks. We prove that there exist general erasure networks for which any conventional routing strategy fails to achieve the optimum diversity-rate trade-off. However, for any general erasure graph, we show that there exists a linear network coding strategy which achieves the optimum diversity-rate trade-off. Unlike the previous works which suggest the potential benefit of linear network coding in the error-free multicast scenario (in terms of the achievable rate), our result demonstrates the benefit of linear network coding in the erasure single-source single-destination scenario (in terms of the diversity gain).

Inom kontexten medelstora svenska icke-finansiella företag är syftet med denna uppsats att undersöka hur sambandet mellan företagens skuldsättningsgrad och företagens sannolikheter för konkurs ser ut genom att tillämpa Byströms Distance to Default (DD). Uppsatsen ämnar besvara följande frågeställningar: (1) Hur ser företagens skuldsättningsgrad och sannolikhet för konkurs ut kvantifierade med Byströms DD? (2) Kan företagen öka andelen främmande kapital utan att nämnvärt öka sannolikheten för konkurs kvantifierat med Byströms DD? En empirisk metod utvecklas för att beräkna företagens skuldsättningsgrad, företagens sannolikhet för konkurs och för att öka andelen främmande kapital utan att nämnvärt öka sannolikheten för konkurs. Indelning av företagen sker på sektornivå. Om uppsatsens frågeställningar kan följande slutsatser dras: (1) företagens skuldsättningsgrad är olika beroende på sektortillhörighet och förändringar i marknadsvärdet av företagens tillgångar och förändringar i volatiliteten av marknadsvärdet av företagens tillgångar har en tydlig påverkan på företagens sannolikhet för konkurs (2) två av sektorerna (i.e. Informationsteknik och Sjukvård) kan öka andelen främmande kapital utan att nämnvärt förändra sannolikheten för konkurs. Tre av sektorerna (i.e. Industrivaror och tjänster, Material och Sällanköpsvaror och tjänster) uppvisar högre skuldsättningsgrader och en tänkbar förklaring är att företagen kortsiktigt avviker från företagens långsiktiga skuldsättningsgrad. När företagens skuldsättningsgrad och sannolikhet för konkurs kvantifieras med Byströms DD uppvisar företag med hög skuldsättningsgrad en högre sannolikhet för konkurs – i enlighet med Trade-Off Theory.

The effects of energy quantity to the reproductive strategies of the sea anemone Aiptasia pulchella Carlgren 1943 Chien-Hsun Chen (Advisors: Drs. Keryea Soong, Chao-Lun Chen) Institute of Marine Biology, National Sun Yat-Sen University, Kaohsiung, 804, Taiwan, R.O.C. Thesis abstract The influences of energy quantity on the sexual and asexual reproduction and possible trade-offs between them in the sea anemone, Aiptasia pulchella were investigated. Different feeding frequencies, light intensities and presence of zooxanthellae were the treatments of energy quantity. Lacerate numbers, lacerate sizes and total weight of lacerates were used to quantify investment in asexual reproduction; oocyte sizes and gonad weights were used as the measures of sexual reproduction. The correlation between total weight of lacerates and that of gonads provided an opportunity for evidence of trade-offs between sexual and asexual reproduction. Under higher feeding frequencies, A. pulchella produced more and larger lacerates as well as larger oocytes and heavier gonads than under lower feeding frequencies. Under lower light intensities, A. pulchella produced more and heavier lacerates with than without zooxanthellae. Lacerate sizes were influenced by light intensities, presence of zooxanthellae and the interaction of the two factors. At intermediate light intensity (2000 lux), Aiptasia pulchella produced heavier gonads than at 0 lux or 10000 lux. A. pulchella produced heavier gonads with than without zooxanthellae. The oocyte sizes of A. pulchella were also influenced by light intensities, zooxanthellae and the interaction of the two. In both sexual or asexual modes of reproduction, A. pulchella performed better under higher than lower feeding frequencies. There were higher level of asexual reproduction for A. pulchella under lower light intensities with zooxanthellae. A. pulchella achieved the highest levels of fecundity, as an indication of sexual reproduction, under a light intensity of 2000 lux in individuals containing zooxanthellae. There is a positive correlation between sexual and asexual investment under different energy regimes. This is not compatible with the prediction of the trade-off hypothesis.

Convergence is a topic that many point to as the driving force behind modern product development. The merger of similar devices into a single product form can create a number of advantages for both producers and consumers, but successful design must take more than just this into account. Convergence is the evolution of a product through a disruptive and uncertain environment of technology and user needs. While the digital revolution has certainly been the biggest recent disrupter to society and design, there are signs of convergence in both form and function that have occurred across many products, and product categories. Producers and consumers always clamor for devices that are useful and convenient, take advantage of the latest technologies, and yet remain intuitive, attractive, and easy to use. This paper will dissect the meaning of convergence in product design and provide a framework for understanding and dialog. Combined with an extensive survey and product mapping, this definition will then be used to delineate approaches and principles for the effective design of evolving products in today's changing environment. The findings of this paper will help designers make decisions when considering the trade-offs between aesthetics, functionality, and ease of use in technology based products.

Comprendre la sélection exercée par la plante hôte et ses conséquences sur la structure des populations pathogènes est essentiel pour gérer durablement les résistances des plantes aux maladies. Les objectifs de ce travail sont i) d'appréhender l'impact de la sélection imposée par des hôtes présentant différents niveaux de résistance, sur la structure phénotypique et génotypique d'une population locale de Phytophthora infestans, agent du mildiou de la pomme de terre ; ii) de déterminer si les pressions de sélection récurrentes exercées par les variétés dominant chaque bassin de production entraînent l'adaptation locale des populations de P. infestans et iii) de tester l'hypothèse d'un trade-off entre agressivité pendant la phase épidémique et capacité de survie hivernale dans des populations clonales de P. infestans. Nos résultats montrent que la sélection par l'hôte agit sur les composantes qualitative (virulence) et quantitative (agressivité) du pouvoir pathogène. La variation importante pour l'agressivité permet une adaptation des populations de P. infestans, pouvant aboutir à l'érosion de résistances partielles. Les populations françaises de P. infestans apparaissent adaptées à la variété dominante nationalement (Bintje), mais pas aux variétés localement dominantes. Le processus d'adaptation locale opère dans ce pathosystème, mais n'est détectable qu'à une échelle spatiale très vaste, pour des populations géographiquement déconnectées. Nos résultats montrent également que lors de la phase de survie hivernale, il n'y a pas de contre-sélection des souches les plus agressives par surmortalité des tubercules infectés. Ce travail souligne l'importance de considérer l'ensemble des forces évolutives pour décrire et comprendre la réponse adaptative des populations pathogènes. La modélisation des processus démogénétiques permettra de proposer et de valider des stratégies de gestion optimales des résistances variétales.

The scope of this thesis was to identify, describe and quantify important life-history traits for the pseudoannual aquatic plant Ranunculus lingua in different ecological settings, by comparing populations from geographically marginal vs. central habitats. Results from a four-year field study showed that abiotic factors (water-level fluctuations and associated processes) tended to have a greater influence in marginal populations, whereas biotic factors (competition, insect grazing and fungal infections) dominated in central populations. This was reflected in different depth distribution of ramet numbers and ramet sizes between the areas, and In different dynamic patterns, with a higher flux of ramets in marginal populations. In a reciprocal transplant experiment, marginal ramets produced more but smaller rhizomes, whereas central ramets produced Individually larger but fewer rhizomes, irrespective of transplant site. A possible selection for genotypes producing large rhizomes in the central habitat was supported by the fact that initially smaller ramets were more likely to be diseased by the fungal pathogen Peronospora gigantea and damaged by insect grazing. In the marginal population, where density-independent mortality factors tend to dominate, a high reproductive output, expressed in production of high numbers of rhizomes, was suggested to be a favoured life-history trait. In a glasshouse experiment, ramets from marginal and central populations were grown in low and high densities and under three contrasting nutrient levels. The allocation to sexual structures was generally very low, and did not incur any costs in terms of reduced rhizome production. Rhizome production showed strong positive allometrical relationships to mother ramet size. Increasing mother ramet size resulted in a larger increase in rhizome numbers for the marginal than for the central population, whereas the increase in mean rhizome mass was more pronounced for the centred population. Both populations showed similar reductions in rhizome production in response to increased density and lowered nutrient levels, which could not be explained by size-dependent effects adone. The dispersal, dynamics and distribution of R. lingua were studied in a marginal river population in northern Sweden, where the only means of dispersal is by vegetative diaspores, i.e. floating rhizome fragments. Stranding occurred mainly in river curves and at obstacles, and the distribution of established stands was also highly correlated with these features. Relative changes in ramet numbers were correlated with water-level fluctuations during the present and previous growing seasons, with winter low-water, and with duration of spring-flood. The predictability of change was high within but low between stands. It was concluded that the patterns and mechanisms of dispersal are fundamental for local distribution patterns as well as variation in regional abundance in R. lingua / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1992, härtill 4 uppsatser</p> / digitalisering@umu

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In large multiprocessors, the access to shared memory is often nonuniform, and may vary as much as ten times for some distributed shared-memory architectures (DSMs). This dissertation identifies another important nonuniform property of DSM systems: nonuniform communication architecture, NUCA. High-end hardware-coherent machines built from large nodes, or from chip multiprocessors, are typical NUCA systems, since they have a lower penalty for reading recently written data from a neighbor's cache than from a remote cache. This dissertation identifies node affinity as an important property for scalable general-purpose locks. Several software-based hierarchical lock implementations exploiting NUCAs are presented and evaluated. NUCA-aware locks are shown to be almost twice as efficient for contended critical sections compared to traditional lock implementations. The shared-memory “illusion”' provided by some large DSM systems may be implemented using either hardware, software or a combination thereof. A software-based implementation can enable cheap cluster hardware to be used, but typically suffers from poor and unpredictable performance characteristics. This dissertation advocates a new software-hardware trade-off design point based on a new combination of techniques. The two low-level techniques, fine-grain deterministic coherence and synchronous protocol execution, as well as profile-guided protocol flexibility, are evaluated in isolation as well as in a combined setting using all-software implementations. Finally, a minimum of hardware trap support is suggested to further improve the performance of coherence protocols across cluster nodes. It is shown that all these techniques combined could result in a fairly stable performance on par with hardware-based coherence.

Organizational Change and Productivity Growth − Evidence from Sweden This paper uses two different firm level surveys matched with employer-employee data to investigate both determinants and effects of different types of organizational change. The results support the competition hypothesis for inducing organizational change. Among the four measures of organizational change investigated in this paper, only delayering shows significant effects on subsequent productivity growth. Firms and Skills: The Evolution of Worker Sorting We document a significant increase in sorting by both cognitive and non-cognitive skill from 1986 to 2008 using data for 28 cohorts of Swedish men. The skill differences within firms have fallen in all major industries while differences in skill between firms have increased. Two main factors drive the increase in sorting. First, workers in high-skilled occupations, such as engineers, have moved to the IT and telecom industries. Second, assortative matching of workers by skill has become more positive. Trading Off or Having it All? Completed Fertility and Mid-career Earnings of Swedish Men and Women Earnings in mid-career and children are two fundamental outcomes of the life-choices of men and women. This paper explores how these outcomes have changed for Swedish men and women born 1945−1962 by documenting changes in education, assortative mating patterns, completed fertility and mid-career earnings and also how the association between children and earnings has changed over time. Solving the Puzzle − Hours Constraints, Technical Change and Female Labor Supply This paper extends the standard theory of labor supply to incorporate an important ingredient in the labor supply decision of today's women: the role of flexibility and time constraints. Using a life-cycle model, I formalize the notion that as technology allows jobs to become more flexible, time constrained individuals can supply more hours and may therefore find it attractive to opt for a more demanding career.

Although research has highlighted the importance of decisions when learning and performing motor actions, few studies have focused on individuals’ ability to choose between potential motor actions. To help bridge this gap, this thesis presents a series of studies that investigate the behaviour of able-bodied individuals when attempting to choose movements based on a speed-accuracy tradeoff. In the first study, a two-alternative forced-choice task was used to determine whether people are consistent with Fitts’s law when choosing the movement they perceive to require the least movement duration. Participants performed almost perfectly when clear visual cues were available—when one of the targets was closer, wider, or both. Contrary to Fitts’s law, however, participants showed a preference for closer targets when visual cues were not informative—when one of the targets was closer and narrower. This study demonstrates that motor decisions are not always optimal, especially when participants are naïve at the task. To determine the basis of individuals’ preference for closer targets, a pair of studies explored the relation between motor decisions, imagined movements, and visual perception. Participants showed a similar deviation from Fitts’s law when imagining movements—believing that movement duration increased with distance within the same index of difficulty. Participants did not behave similarly, however, in a perceptual version of the decision task. These results suggest that imagined movements and motor decisions are linked, but they are not always based on veridical representations of actual movement. To further probe the origin of individuals’ erroneous belief about movement duration, the final study of this thesis measured movement duration for movements made at speeds other than ‘as fast as possible’. Movements made at more natural movement speeds shared important similarities with decisions and imagined movements. This study suggests that the biases seen in naïve motor decisions might originate from participants considering movements for which they have more experience, such as target-directed movements made at a naturally-selected pace. Together, the findings presented in this thesis may help to identify the ways that motor decisions can deviate from optimal, suggesting how those decisions must change with practice to better accomplish a task.