This dissertation studies several problems centered around developing a better understanding of the energy efficiency of cooperative wireless communication systems. Cooperative communication is a technique where two or more nodes in a wireless network pool their antenna resources to form a "virtual antenna array". Over the last decade, researchers have shown that many of the benefits of real antenna arrays, e.g. spatial diversity, increased range, and/or decreased transmission energy, can be achieved by nodes using cooperative transmission. This dissertation extends the current body of knowledge by providing a comprehensive study of the energy efficiency of two-source cooperative transmission under differing assumptions about channel state knowledge, cooperative protocol, and node selfishness. The first part of this dissertation analyzes the effect of channel state information on the optimum energy allocation and energy efficiency of a simple cooperative transmission protocol called "orthogonal amplify-and-forward" (OAF). The source nodes are required to achieve a quality-of service (QoS) constraint, e.g. signal to noise ratio or outage probability, at the destination. Since a QoS constraint does not specify a unique transmit energy allocation when the nodes use OAF cooperative transmission, minimum total energy strategies are provided for both short-term and long-term QoS constraints. For independent Rayleigh fading channels, full knowledge of the channel state at both of the sources and at the destination is shown to significantly improve the energy efficiency of OAF cooperative transmission as well as direct (non-cooperative) transmission. The results also demonstrate how channel state knowledge affects the minimum total energy allocation strategy. Under identical channel state knowledge assumptions, the results demonstrate that OAF cooperative transmission tends to have better energy efficiency than direct transmission over a wide range of channel conditions. The second part of this dissertation focuses on the development of an opportunistic hybrid cooperative transmission protocol that achieves increased energy efficiency by not only optimizing the resource allocation but also by selecting the most energy efficient cooperative transmission protocol from a set of available protocols according to the current channel state. The protocols considered in the development of the hybrid cooperative transmission protocol include compress-and-forward (CF), estimate-and-forward (EF), non-orthogonal amplify-and-forward (NAF), and decode-and-forward (DF). Instantaneous capacity results are analyzed under the assumption of full channel state knowledge at both of the sources and the destination node. Numerical results are presented showing that the delay limited capacity and outage probability of the hybrid cooperative transmission protocol are superior to that of any single protocol and are also close to the cut-set bound over a wide range of channel conditions. The final part of this dissertation focuses on the issue of node selfishness in cooperative transmission. It is common to assume in networks with a central authority, e.g. military networks, that nodes will always be willing to offer help to other nodes when requested to do so. This assumption may not be valid in ad hoc networks operating without a central authority. This section of the dissertation considers the effect selfish behavior on the energy efficiency of cooperative communication systems. Using tools from non-cooperative game theory, a two-player relaying game is formulated and analyzed in non-fading and fading channel scenarios. In non-fading channels, it is shown that a cooperative equilibrium can exist between two self-interested sources given that the end of the cooperative interaction is uncertain, that the sources can achieve mutual benefit through cooperation, and that the sources are sufficiently patient in the sense that they value future payoffs. In fading channels, a cooperative conditional trigger strategy is proposed and shown to be an equilibrium of the two-player game. Sources following this strategy are shown to achieve an energy efficiency very close to that of a centrally-controlled system when they are sufficiently patient. The results in this section show that cooperation can often be established between two purely self-interested sources without the development of extrinsic incentive mechanisms like virtual currency.

Three general questions are studied regarding plant carbon allocation strategies. (1) The R* Rule states that the superior competitor in a plant community should exclude all others by minimizing available limiting nutrient concentration below the level needed for survival of its competitors. I asked whether a plant carbon allocation strategy that minimizes the concentration of available limiting nutrient is consistent with Lotka's (1922) conjecture that ecosystems should evolve to maximize total energy flow (primary production). (2) In landscapes such as the Everglades, areas of landscape with higher energy flow (primary production) than the surrounding area also have higher available concentrations of limiting nutrient, rather than lower concentrations, which might be expected from the R* rule. I asked whether this pattern can be explained. (3) I asked how optimal allocation of carbon to plant defense allocation strategies might depend on different conditions of nutrient availability, shading, and herbivory. To address all three questions, I used a model revised from the G'DAY model (Comins and McMurtrie 1993) to study tree allocation of carbon resources between foliage, roots, and defense. With regard to the first question, I found that the allocation strategy that leads to minimum concentration of available nutrients is the same as the strategy for which energy flux to roots, rather than total energy flux, is maximized. Further, I found that the strategy that was competitively dominant was neither the strategy for which total energy flux was maximized, nor that for which available nutrient concentration was minimized. With regard to the second question, I found that, if a patch of vegetation on a landscape is able to capture nutrients from the surrounding landscape, for example, through relatively higher evapotranspiration, it could lead to the opposite of what is expected from the R* rule; that is, available limiting nutrient concentration is maximized when carbon flow to the roots is maximized. With regard to the last question, I found that under high herbivory, the optimal plant strategy for allocation of carbon to defense depends on the available nutrient concentration and amount of radiation to the plant, in agreement with some theoretical predictions.

Resting metabolic rate (RMR) represents the lowest level of aerobic metabolism in a resting individual. By contrast, maximal metabolic rate (MMR) reflects the upper limit of aerobic metabolism achieved during intensive exercise. As RMR and MMR define the boundaries of the possible levels of metabolism expressed by a normothermic individual, a key question is whether RMR and MMR are correlated. To evaluate the relationship between RMR and MMR, I took repeated paired measurements of RMR and MMR on 165 white-footed mice (Peromyscus leucopus) during the summer of 2018. Repeatability (R±se) was significant for both RMR and MMR (RRMR=0.15±0.07 and RMMR=0.27±0.12). At the residual level (within-individual), RMR and MMR were significantly and positively correlated (re=0.20, 95% confidence intervals: 0.04, 0.34). Such a positive residual correlation could be result of correlated phenotypic plasticity. By contrast, RMR and MMR were significantly and negatively correlated at the among-individual level (rind=-0.87, 95% confidence intervals: -0.99, -0.28). The negative among-individual correlation suggests there are trade-offs between the maintenance and active components of the energy budget (allocation model). Future research should investigate the relationship between RMR and other energetically expensive behaviours and activities to understand how energy is allocated among individuals.

This study addresses the nature of physiological and phenological evolutionary strategies of root growth dynamics and energy allocation followed by Atriplex confertifolia, Ceratoides lanata, and Artemisia tridentata growing in their natural cool desert environment. Root observation chambers with inclined Plexiglass windows were installed in monospecific desert communities of Atriplex confertifolia, Ceratoides lanata and Artemisia tridentata. Soil temperature and water potential measurements taken immediately adjacent to the observation windows indicated a minimal disturbance was caused by the presence of these chambers. For the three species initiation of root growth was observed before initiation of shoot activity, furthermore, active root growth extended over much longer periods during the year than shoot growth. Initial growth was observed for the three species in the upper soil layers in the spring. Later in the season most of the growth activity was measured at progressively greater depths in the soil. Measurable root growth was observed for Atriplexin August when the soil water potentials were in the range of -70 bars for 1972, and at water potentials of -60 bars for all three species during 1973. Detectable growth for these three species was recorded as late as January in 1974. Except for the main extension roots, individual apical meristems were seldom active for more than 2 weeks. Atriplex confertifolia and Ceratoides lanata plots were labeled during the growth season with 14Co2 in polyethylene enclosures to study both the partitioning of photosynthates to plant parts and their total allocation of carbon at the community level. A definite seasonal pattern of partitioning of recent photoassimilates corresponding to phenological events emerged. In the spring, photoassimilates were principally directed to shoot growth, especially expanding new leaves and vegetative buds. In terms of relative energy allocated to plant parts per unit dry weight basis, it appears that Ceratoides lanata expends less energy for reproductive organs. For both species, carbon used for new stems and previous years shoot growth appears to constitute a significant sink for energy use and storage. Relative translocation of carbon to roots was minimal during the spring for both species. It increased with the progression of the season reaching a maximum in July for Atriplex and at the end of the season for Ceratoides. Energy allocation at the community level for these species showed that approximately 60 and 40 percent of the recently photoassimilated 14C for the Atriplex-dominated community in July and September, respectively, appeared localized in the new shoot growth, the remaining was distributed in nearly equal amounts between previous year's shoot growth and the root system. The scheme of energy allocation in Ceratoides showed similar patterns of carbon utilization in July and September; approximately 80 percent of the fixed carbon was al located in approximately equal amounts to roots and new shoot growth with the remainder to the previous year's shoot growth. In the Ceratoides-dominated community 65 percent and 36 percent of 14C photoassimilated in April and July, respectively, and still remaining in the plant by September, was localized in the underground structures. Similarly, in the Atriplex community, 35 percent and 29 percent of the 14C incorporated in April and July appeared in the root system. From the total 14C photoassimilated in July for both communities, approximately 60 percent and 50 percent was retained in the plants by September in the Atriplex- and Ceratoides-dominated communities, respectively.

Les polychlorobiphényles (PCB) et les polybromodiphényléthers (PBDE) sont deux familles de composés hydrophobes partageant certaines propriétés physico-chimiques. Des travaux antérieurs ont montré que ces composés pouvaient affecter les traits d’histoire de vie des poissons. Il s’avère cependant que les études approchant des situations environnementales sont rares. Cette thèse se divise en trois parties. La première partie s’est attachée à évaluer les effets d’une exposition à un mélange réaliste de PCB et de PBDE sur les traits d’histoire de vie du poisson-zèbre. Les résultats ont montré une taille asymptotique plus élevée, une probabilité de ponte retardée chez les individus exposés et une faible survie des larves F1 en situation de jeûne issues des pontes précoces des individus exposés. La seconde partie a cherché à identifier, sur la base d’un modèle bioénergétique (DEB), les modes d’action physiologique (PMoA) de PCB et PBDE. Deux PMoAs probables ont été révélés: le premier est lié à l’augmentation de la fraction d’énergie allouée à la maintenance et la croissance somatique et le deuxième est lié à l’augmentation des coûts de production d’un œuf. La troisième partie de la thèse s’est intéressée à évaluer les conséquences de la contamination sur la dynamique de population de poissons. Les résultats ont montré une réduction de l’abondance numérique, une augmentation de la biomasse et un grand risque de surexploitation chez la population exposée, Les résultats de cette thèse pourraient constituer un outil d’aide à une gestion durable des stocks halieutiques qui prennent en compte les effets de multiples contaminations qui se surajoutent à la pression de pêche. / Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are two families of hydrophobic compounds sharing some similar environmental properties. Previous studies have demonstrated that these compounds could affect fish life-history traits. However, few studies have focused on environmental situations. This thesis is divided into three parts. The first part aimed to evaluate the effects of a realistic mixture of PCBs and PBDEs on the life-history traits of zebrafish. The results showed a slower growth, but to a larger asymptotic length, and delayed spawning probability in exposed fish. In addition, offspring issued from early spawning events of exposed fish exhibited a lower larval survival under starvation condition. The second part aimed to identify, on the basis of a bioenergetic model (DEB), the physiological modes of action (PMoA) of PCBs and PBDEs. Two potential PMoAs have been revealed: the first one was through an increase of the fraction of energy allocated to somatic maintenance and growth and the second one was through an increase of the cost of production of an egg. The third part focused on the population dynamical consequences of the individual life-history effects of PCBs and PBDEs. The results showed a lower abundance, a higher biomass and a higher risk of overexploitation in exposed population compared to control population. The results of this thesis could be a helpful tool for sustainable management of fish stocks that take into account the effects of multiple contaminations that are added to the fishing pressure.

It has been shown that fish of both marine and limnetic origin display increased growth at intermediate salinities. Furthermore, it has been shown that fish in the brackish water Baltic Sea are smaller compared to their conspecifics in the Atlantic, where salinities are higher. Also, it has been suggested that fish produce more eggs at the edges of their distribution range as a response to inferior environmental conditions. In this study, I investigated if there is a trade-off in energy investment between somatic and gonad growth in relation to salinity. To do this, I performed a growth experiment and a literature review. In the growth experiment, juvenile turbot were reared in salinities of 6, 10.5, 15 and 30 ‰. I found that turbot juveniles from Gotland grew equally well in all salinities investigated. In the literature review, data from the Baltic Sea was tested against data from the North and Black Seas. Data of turbot total energy investment (somatic and gonad growth) was analyzed. I found that energy content at age differed significantly between the populations investigated with lower energy content for the Baltic Sea populations. Also, growth rate in relation to energy content (size) was analyzed for the different populations, but no difference for growth rate in relation to energy content occurred. The result of the analysis of growth rate indicates that the change in allocated energy is the same, regardless of population, and thus that fish from the Baltic Sea display growth rates similar to those of other populations. It was also established that energy investment in gonads increased along with decreasing salinities. The smaller size of turbot in the Baltic Sea is therefore probably the result of a difference in size at maturity, possibly because less energy is allocated to somatic growth and more energy to start producing eggs. It is probably also the consequence of that the Baltic Sea turbot, post sexual maturity, continue to invest more energy in egg production.

For acquisition of narrow-beam free-space optical (FSO) terminals, a Global Positioning System (GPS) is typically required for coarse localization of the terminal. However, the GPS signal may be shadowed, or may not be present at all, especially in rough or unnameable terrains. In this study, we propose a lidar-assisted acquisition of an unmanned aerial vehicle (UAV) for FSO communications in a poor GPS environment. Such an acquisition system consists of a lidar subsystem and an FSO acquisition subsystem: The lidar system is used for coarse acquisition of the UAV, whereas, the FSO system is utilized for fine acquisition to obtain the UAV’s accurate position. This study investigates the optimal allocation of energy between the lidar and FSO systems to minimize the acquisition time. Here, we minimize the average acquisition time, and maximize the cumulative distribution function of acquisition time for a fixed threshold. We learn that an optimal value of the energy allocation factor exists that provides the best performance of the proposed system.

No description available.

This dissertation develops optimal algorithms for distributed detection and estimation in static and mobile sensor networks. In distributed detection or estimation scenarios in clustered wireless sensor networks, sensor motes observe their local environment, make decisions or quantize these observations into local estimates of finite length, and send/relay them to a Cluster-Head (CH). For event detection tasks that are subject to both measurement errors and communication errors, we develop an algorithm that combines a Maximum a Posteriori (MAP) approach for local and global decisions with low-complexity channel codes and processing algorithms. For event estimation tasks that are subject to measurement errors, quantization errors and communication errors, we develop an algorithm that uses dithered quantization and channel compensation to ensure that each mote's local estimate received by the CH is unbiased and then lets the CH fuse these estimates into a global one using a Best Linear Unbiased Estimator (BLUE). We then determine both the minimum energy required for the network to produce an estimate with a prescribed error variance and show how this energy must be allocated amongst the motes in the network. In mobile wireless sensor networks, the mobility model governing each node will affect the detection accuracy at the CH and the energy consumption to achieve this level of accuracy. Correlated Random Walks (CRWs) have been proposed as mobility models that accounts for time dependency, geographical restrictions and nonzero drift. Hence, the solution to the continuous-time, 1-D, finite state space CRW is provided and its statistical behavior is studied both analytically and numerically. The impact of the motion of sensor on the network's performance is also studied.

Les théories relatives à la biodiversité contrastent fortement quant au rôle qu’elles accordent aux différences de traits écologiques entre espèces (théorie des niches) ou à la stochasticité démographique (théorie neutre de la biodiversité) pour expliquer l’organisation des communautés d’espèces compétitrices. Les espèces en compétition pour une ressource pulsée permettent de tester à relativement court terme ces théories : dans le cadre de la théorie des niches, les espèces en compétition devraient présenter de fortes différences de traits les conduisant à exploiter différemment la ressource pulsée; elles devraient alors répondre démographiquement de manière différente aux fortes fluctuations en ressources et leurs dynamiques populationnelles devraient être asynchrones. Au contraire, dans le cadre de la théorie neutre, les espèces ne devraient pas présenter de différences majeures dans leurs caractères associés à l’exploitation de la ressource variable; elles devraient alors répondre de la même manière aux pulses et leurs dynamiques populationnelles devraient être synchronisées. Nos travaux, centrés sur quatre espèces du genre Curculio en compétition pour l’exploitation des glands de chêne, permettent de mettre en évidence (i) qu’un fort partitionnement global de leurs niches est assorti de dynamiques populationnelles asynchrones. (ii) Cependant, ils montrent également que deux des quatre espèces compétitrices apparaissent très similaires quant aux caractères étudiés et présentent des dynamiques de population synchronisées. Les résultats, dans leur ensemble, fournissent donc l’un des premiers arguments empiriques en faveur d'une théorie unifiée de la biodiversité / Understanding the organization of communities composed of competing species, and notably their biodiversity, has led to two theories that sharply contrast with each other about the role primarily assigned either to the differences in ecological traits among the species (niche theory) or to the demographic stochasticity (neutral theory of biodiversity). Species competing for a pulsed resource allow testing the two theories in short-term studies: the niche theory predicts that differences should exist in the traits of such species, which should allow them taking advantage of the resource in various ways; the species should thus respond differently to the fluctuations in the availability of the resource, resulting in asynchronous population dynamics. In contrast, the neutral theory predicts that the trait differences possibly existing between the species should not impact the way they use the variable resource; the species should then respond similarly to the pulses and their population dynamics should be synchronized. Our work, focusing on four phytophagous insect species (Curculio spp.) that compete for oak acorns (Quercus spp.), (i) show evidence of a clear, global niche partitioning combined with asynchronous population dynamics (ii) but points out that two of these species show similar ecological traits and display synchronized population dynamics. Overall, these results therefore provide one of the first empirical arguments in favor of a unified theory of biodiversity