Given Number Of Levels Research Articles

Selection of Optimal Deployment and Routing Configurations in Underwater Acoustic Sensor Networks for Avoiding Energy Holes

Improving the energy efficiency of underwater acoustic sensor networks (UW-ASNs) is a crucial issue due to the reduced and nonrechargeable energy resource of the underwater sensor nodes. In this work, we address the energy sink hole problem in UW-ASNs while considering the unique and harsh characteristics of the underwater channel. Our goal is to determine the optimal deployment and routing settings that surmount the energy sink hole problem and hence maximize the network lifetime. We prove that sensors can evenly consume their initial battery power provided that first they adjust their transmission power when they transmit the route through traffic and second they are appropriately placed while deployed. Mainly, we propose a deployment scheme and the corresponding balanced routing strategy that lead to uniform energy consumption among all underwater sensors subject to a predefined reliability level at the sink. Specifically, we look for the optimal deployment settings especially in terms of nodes’ separation distances that help achieving uniform energy consumption in the network while satisfying the application requirement especially in terms of desired information reliability. Jointly, at the routing layer, we assume that each sensor is provided with the possibility of dynamically adjusting its transmission power up to a given number of levels N. To this goal, we mainly deal with two main cases: fixed and variable nodes separation distance. For the fixed case, we suppose that any two successive nodes in the network are equally spaced, and we strive for deriving the optimal distance as well as the optimal number of transmission power levels along with optimal load weight corresponding to every possible transmission power level for every sensor node. For the variable case, we deal with two subcases: first, we suppose that the distance separating successive nodes follows an arithmetic progression, and second, we assume that the distance separating successive nodes is following a geometric sequence. Note that for both cases, namely, fixed and variable, we succeed to determine the optimal distances separating successive nodes and the optimal number N of transmission power levels along with the corresponding optimal load weight that overcome the energy holes problem, and hence the network lifespan is maximized while respecting the desired reliability level.

An engineering, multiscale constitutive model for fiber‐forming collagen in tension

This work proposes a nonlinear constitutive model for a single collagen fiber. Fiber-forming collagen can exhibit different hierarchies of basic units, called fascicles, bundles, fibrils, microfibrils, and so forth, down to the molecular (tropocollagen) level. Exploiting the fact that at each hierarchy level the microstructure can be seen, at least approximately, as that of a wavy, or crimped, extensible cable, the proposed stress-strain model considers a given number of levels, each of which contributes to the overall mechanical behavior according to its own geometrical features (crimp, or waviness), as well as to the basic mechanical properties of the tropocollagen. The crimp features at all levels are assumed to be random variables, whose statistical integration furnishes a stress-strain curve for a collagen fiber. The soundness of this model-the first, to the Authors' knowledge, to treat a single collagen fiber as a microstructured nonlinear structural element-is checked by its application to collagen fibers for which experimental results are available: rat tail tendon, periodontal ligament, and engineered ones. Here, no attempt is made to obtain a stress-strain law for generic collagenous tissues, which exhibit specific features, often much more complex than those of a single fiber. However, it is trivial to observe that the availability of a sound, microstructurally based constitutive law for a single collagen fiber (but applicable at any sub-level, or to any other material with a similar microstructure) is essential for assembling complex constitutive models for any collagenous fibrous tissue.

Hybrid Multilevel Converters: Unified Analysis and Design Considerations

The concept of hybrid multilevel converters has been generalized for different arrangements of direct-current voltage levels, modulation strategies, topologies of series-connected cells, and/or semiconductor technologies to optimize the power processing of the overall system. Therefore, a given number of levels can be synthesized by several multilevel configurations, significantly increasing flexibility and complexity in the design of hybrid multilevel converters. However, a generalized design methodology to define the main parameters of these topologies for distinct design criteria has not yet been presented. To overcome this lack, this paper presents a comparative analysis among various hybrid multilevel topologies, and it proposes some design considerations for distinct applications. Consequently, this paper constitutes a useful basis for defining an adequate hybrid arrangement for any application