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Vukovic, Milos, Roland Leifeld, and Hubertus Murrenhoff. "STEAM – a hydraulic hybrid architecture for excavators." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200445.
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During the past three years the Institute for Fluid Power Drives and Controls in Aachen has developed a new hydraulic system for mobile machinery called STEAM. The system represents a new step in excavator hydraulics, as it aims to reduce both the hydraulic system losses as well as those of the internal combustion engine by using a hybrid hydraulic architecture with accumulators. Starting with initial simulation studies the development has been followed by scaled test bench measurements and has progressed to a full scale validation using an 18 t excavator. The following publication aims to summarise the results obtained thus far with the aim of making them available to industry and encouraging their implementation in future applications.
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Jleilaty, Subhi. "Control Architecture for Electro-Hydraulic Humanoid Robot." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST010.
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Malgré les progrès significatifs réalisés jusqu'à présent dans le contrôle des robots humanoïdes, ceux-ci sont encore loin de présenter de manière fiable des comportements semblables à ceux des humains. Les différents éléments qui composent les humanoïdes contribuent à l'amélioration de leurs comportements. Alors que l'augmentation de la limitation physique contribue aux mouvements dynamiques, l'architecture de contrôle est la clé pour gérer ces mouvements et déterminer les capacités du robot afin d'améliorer ses comportements. Ce travail vise à développer une architecture de contrôle émulant la fonctionnalité du système nerveux humain. Les architectures classiques traitaient des cycles sensorimoteurs mais sans distribution de l'intelligence. Qu'elles soient centralisées, où tous les composants sont connectés à une unité centrale, ou décentralisées, où les unités distribuées servent d'interface entre les E/S et le contrôleur principal sans pouvoir prendre de décision. La solution proposée est une architecture de contrôle en temps réel distribuée avec ROS. Les contrôleurs conjoints ont l'intelligence de prendre des décisions, de dominer leurs actionneurs et de publier leur état. Les validations expérimentales ont été effectuées sur notre robot humanoïde électro- hydraulique (HYDROïD). Les résultats démontrent des avancées de 50 % dans le taux de mise à jour par rapport à d'autres humanoïdes et de 30 % dans la latence du processeur principal et des tâches de contrôle. L'architecture proposée permet de créer et de tester des systèmes à intelligence artificielle distribuée<br>Despite the significant improvements achieved until now in controlling humanoid robots, they are still a long way from reliably exhibiting human-like behaviors. Various components that formulate humanoids contribute to improving their behaviors. While increasing the physical limitation contributes to dynamic motions, the control architecture is the key to managing those motions and determining robot capabilities to improve its behaviors. This work aims to develop a control architecture emulating the functionality of the human nervous system. Classical architectures dealt with sensorimotor cycles but without intelligence distribution. Whether centralized, where all components are connected to a central unit, or decentralized, where the distributed units are used as an interface between the I/Os and the master controller with no ability to make a decision. The proposed solution is a distributed real-time control architecture with ROS. The joint controllers have the intelligence to make decisions, dominate their actuators, and publish their state. The real- time capabilities are ensured in the master controller by using a Preempt-RT kernel beside OROCOS middleware to operate the real-time tasks. And in the customized joint controllers by FreeRTOS firmware. The experimental validations were performed on our electro-hydraulic humanoid robot (HYDROïD). The results demonstrate 50% advancements in the update rate compared to other humanoids and 30% in the latency of the master processor and the control tasks. The proposed architecture gives the possibility to create and test the systems with distributed artificial intelligence
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Boulineau, Sheryl Taillon. "East Lake Meadows : hydrologic strategies for architecture." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/23366.
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Pingarrón, Alvarez Victoria I. "Performance analysis of hydraulic lime grouts for masonry repair." Connect to PDF file, 2006. http://repository.upenn.edu/cgi/viewcontent.cgi?article=1013&context=hp_theses.
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Ammounah, Anas. "Architecture de contrôle pour un robot humanoïde à actionnement hydraulique." Electronic Thesis or Diss., université Paris-Saclay, 2021. http://www.theses.fr/2021UPASG056.
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HYDROïD est le premier robot humanoïde à actionnement hydraulique en Europe. Cette plateforme de recherche a été créée pour émuler le corps humain. L'émulation du corps humain est importante car l'objectif du robot humanoïde du futur est de coopérer et d'interagir avec les humains, voire de les remplacer dans des scénarios dangereux. Cette interaction nécessite des aspects de sécurité. L'émulation et le fait de disposer d'un robot anthropomorphe comme le corps humain simplifient la réalisation de cet objectif. De nombreux aspects de l'émulation ont déjà été réalisés, l'actionnement du robot émule les muscles humains, les mécanismes hybrides émulent la cinématique humaine et l'effet agoniste-antagoniste, la conception mécanique du robot émule la morphologie fine et la distribution de masse du corps humain, et le flux hydraulique émule le flux sanguin à l'intérieur du corps.Dans cette thèse, nous avons cherché à émuler l'architecture du système nerveux humain, c'est-à-dire la structure physique, la transmission et le traitement de l'information. Nous avons proposé une architecture de contrôle en couches pour HYDROïD. Une architecture distribuée avec 12 contrôleurs locaux a été conçue pour être placée sur le corps du robot afin de contrôler 36 articulations cinématiques actionnées hydrauliquement. Un PC central doté d'un système d'exploitation en temps réel gère le mouvement du corps entier par le biais d'un intergiciel en temps réel et de la communication EtherCAT. Chaque contrôleur local est une unité informatique intégrée complète permettant de contrôler le robot au niveau des articulations. Un pilote personnalisé a été construit pour contrôler l'actionnement hydraulique. Nous avons étudié deux approches à ce niveau, en utilisant une approche à boucle unique et une approche multithreading<br>HYDROïD is the first humanoid robot with hydraulic control in Europe. This research platform was created to emulate the human body. The emulation of the human body is important because the objective of the humanoid robot in the future is to cooperate and interact with humans, and even to replace them in dangerous scenarios. This interaction requires safety aspects. Emulation and having an anthropomorphic robot like the human body simplifies the achievement of this goal. Many aspects of emulation have already been realized, the actuation of the robot emulates human muscles, the hybrid mechanisms emulate human kinematics and agonist-antagonist effect, the mechanical design of the robot emulates the thin morphology and mass distribution of the human body, and the hydraulic flow emulates the blood flow inside the body.In this thesis, we have sought to emulate the architecture of the human nervous system, i.e., the physical structure, transmission, and processing of information. We proposed a layered control architecture for HYDROïD. A distributed architecture with 12 local controllers has been designed to be placed on the body of the robot to control 36 hydraulically operated kinematic joints. A central PC with a real-time operating system manages the whole-body motion through real-time middleware and EtherCAT communication. Each local controller is a complete integrated computing unit to control the robot at the joint level. A custom driver was built to control the hydraulic actuation. We investigated two approaches at this level, using a single-loop approach and a multi-threading approach
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Vinya, Royd. "Stem hydraulic architecture and xylem vulnerability to cavitation for miombo woodlands canopy tree species." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:9028b995-5379-4969-8a7b-59a7aa7ab533.
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Africa's miombo woodlands constitute one of the most important dry tropical forests on earth, yet the hydraulic function of these woodlands remains poorly researched. Given the current predictions of increased aridity by the end of this century in the miombo ecoregion, understanding the likely response of miombo woodlands tree species to water stress is crucial in planning adaptation strategies. Predicting the response of miombo woodlands to future climate trends is hampered by a lack of knowledge on the physiology of the common miombo woodlands tree species. In particular, plant-water relations for this woodlands type are not well understood. An understanding of plant-water relations for this woodlands type will provide insights into how water limits tree species distribution in this ecosystem. This will also improve our prediction model on the likely response of this ecosystem to predicted climate change. For this reason, the overall objective of this research was to evaluate the hydraulic architecture and xylem vulnerability to cavitation for nine principal miombo woodlands tree species differing in drought tolerance ability and habitat preference. This was achieved by; examining the hydraulic properties and evaluating the extent to which each hydraulic design was vulnerable to water stress-induced xylem cavitation; investigating how seasonal changes in plant-water relations influences seasonal patterns of leaf display and; analyzing the relationship between stem hydraulic supply and leaf functional traits related to drought tolerance ability. This research has found that drought-intolerant tree species with mesic specialization have more efficient stem hydraulic systems than co-occurring habitat broad ranging species. Broad ranging tree species attain wider habitat distribution by adjusting their hydraulic supply in response to changing ecosystem water availability. The finding that hydraulic properties differ significantly between tree species with contrasting habitat preference suggests that tree hydraulic design may have some adaptive ecological role in influencing species habitat preferences in miombo woodlands. The evaluation of xylem vulnerability to cavitation revealed that mesic specialized tree species were more vulnerable to water stress-induced cavitation than habitat broad ranging tree species. Vulnerability to cavitation in individuals from the same broad-ranging species growing in contrasting habitats showed only marginal and statistically insignificant (P > 0.05) differences between wet and dry sites. In the investigation of the influence of seasonal changes in stem water relations on seasonal leaf display, seasonal rhythms in stem water status were found to exert significant controls on leaf phenology. Mesic specialists had strong stem water controls throughout the year in comparison to broad ranging tree species. An analysis of the relationship between stem hydraulic supply and leaf functional traits suggests that stem hydraulic supply constrains leaf biomass allocation patterns among miombo tree species. Mesic specialists tend to invest more in leaf longevity than broad ranging tree species. This thesis has uncovered some interesting relationships between plant-water-relations and the distribution of miombo woodlands tree species. These results lead to the conclusion that in an event of increased ecosystem drying under future climate trends, tree species with mesic specialisation are at a greater risk of experiencing cavitation related species mortality than broad ranging ones.
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Lechthaler, Silvia. "The hydraulic architecture of the plants: study of the allometric relations in stem and leaves." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3426838.
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The xylem in plants is formed by interconnected dead cells that allow the flow of water from the roots to the leaves. The ascent of sap is mainly passive and it is driven by water evaporation from the mesophyll cell walls in the leaf. The water evaporation generates capillary suction on the menisci at the micro-porous of cell walls, causing negative hydrostatic pressure that propagates down the water column in the xylem. Due to plants grow in height the length of the hydraulic path increases progressively posing the question whether the hydraulic resistance increases accordingly. There is evidence that plants have evolved xylem structures that compensate the possible increase of the hydraulic resistance imposed by path length, namely the tip-to-base conduits widening. Conduits widening has been reported in several species, both angiosperms and conifers, showing that the degree of widening from tip to the base of the stem is very similar among species, or in other words, that plants converge towards a universal xylem structure. Nevertheless, several points on the hydraulic architecture of plants remain to be elucidated.
A largely debated point is whether xylem anatomical traits (e.g. the absolute cell size) change with climatic conditions. Moreover, whether and how the conduits widening in the stem may affect the xylem anatomy of the leaf is still not fully understood. This PhD project aims to widen our understanding of the allometric relations of leaves and stem xylem, considering how the environmental conditions and the height of the plant affect the hydraulic architecture of the water transport system.
A methodological study (Study 1) has been performed on the xylem tissue of stems of Acacia trees grown in different water availability conditions. The main result was that, once the anatomical data were standardized for the tree height, the hydraulic architecture of the xylem did not change in relation to the environmental conditions.
Two studies have been performed on the hydraulic architecture of leaves. The main focus was on the anatomical traits of the xylem conduits in relation to the leaf dimensions and/or the position in the tree crown (height from the base of the stem). The main results were that the xylem traits scaled with the leaf area independently by the position in the crown (Study 2). A fine analysis of the leaf midrib (i.e. major leaf vein) has shown a rigid hydraulic architecture and tissues coordination (Study 3) that was well predicted by the distance from the leaf tip. Both studies showed that the dimensions of the terminal veins were conserved among leaves and within leaf suggesting that the hydraulic architecture of the xylem in the leaf evolved in a way to guarantee an equal distribution of the hydraulic resistances (and thus of the water) among leaves and within the leaf lamina.
Finally, we implemented the anatomical data of both stem and leaf into a hydraulic model to assess the distribution of resistances along the hydraulic path to evaluate how the anatomy of the transport system affects the physiology of the entire tree (Study 4).
This thesis has highlighted that the path length (i.e. the height of the plant and the dimensions of the leaf) is the main factor affecting the hydraulic architecture of the tree. The conduit dimension in both stem and leaf are determined by the distance from the terminal parts, stem apex or leaf tip respectively. Climatic conditions resulted to have marginal (non-significant) effect on the stem anatomical traits. In the leaf, the dimensions of the xylem conduits are statistically invariant with changes in plant size. This rigid hydraulic architecture of the tree, from the stem to the leaf, allows minimizing the effect of the path length on the hydraulic resistance, confining nearly the whole gradient of water potential within the leaves.<br>Lo xilema nelle piante è formato da cellule morte interconnesse che consentono il flusso di acqua dalle radici alle foglie. L'ascesa della linfa è principalmente passiva ed è guidata dall'evaporazione dell'acqua dalle pareti cellulari del mesofillo nella foglia. L'evaporazione dell'acqua genera un'aspirazione capillare sui menischi a livello dei micro-pori delle pareti cellulari, causando una pressione idrostatica negativa che si propaga lungo la colonna d'acqua nello xilema. A causa dell’aumento in altezza delle piante, la lunghezza del percorso idrico aumenta progressivamente ponendo la domanda se la resistenza idraulica aumenta di conseguenza. Vi è evidenza che le piante hanno evoluto strutture xilematiche che compensano il possibile aumento della resistenza idraulica imposta dall'aumento della lunghezza del percorso, come ad esempio l'allargamento dei condotti dalla punta alla base. L’allargamento dei condotti è stato osservato in diverse specie, sia angiosperme sia conifere, dimostrando che il grado di allargamento dalla punta alla base dello stelo è molto simile tra le specie, o in altre parole, che le piante convergono verso una struttura xilema universale. Tuttavia, restano da chiarire diversi punti sull'architettura idraulica delle piante.
Un punto largamente dibattuto è se tratti anatomici dello xilema (ad esempio la dimensione assoluta delle cellule) cambiano con le condizioni climatiche. Inoltre, se e come i condotti che si allargano nello stelo possano influenzare l'anatomia dello xilema della foglia non è ancora completamente compreso. Il progetto di questo dottorato mira ad ampliare la nostra comprensione delle relazioni allometriche nello xilema delle foglie e del fusto, considerando come le condizioni ambientali e l'altezza della pianta possano influenzare l'architettura idraulica del sistema di trasporto dell'acqua.
Uno studio metodologico (Studio 1) è stato eseguito sul tessuto xilematico di fusti di alberi di acacia cresciuti in diverse condizioni di disponibilità idrica. Il risultato principale è stato che, una volta che i dati anatomici sono stati standardizzati per l'altezza dell'albero, l'architettura idraulica dello xilema non è cambiata in relazione alle condizioni ambientali.
Sono stati eseguiti due studi sull'architettura idraulica delle foglie. L'obiettivo principale degli studi riguardava i tratti anatomici dei condotti dello xilema in relazione alle dimensioni della foglia e / o alla posizione nella chioma dell'albero (altezza dalla base del fusto). Dai risultati si evince che i tratti dello xilema si ridimensionano in base all'area fogliare indipendentemente dalla posizione nella chioma (Studio 2). Un'analisi fine della nervatura principale della foglia ha mostrato una rigida architettura idraulica e la coordinazione dei tessuti (Studio 3), ben predetta dalla distanza dalla punta della foglia. Entrambi gli studi hanno dimostrato che le dimensioni delle vene terminali sono conservate tra le foglie e all'interno della stessa foglia, suggerendo che l'architettura idraulica dello xilema si è evoluta in modo da garantire distribuzione omogenea delle resistenze idrauliche (e quindi dell'acqua) tra le foglie e lungo la lamina fogliare.
Infine, abbiamo implementato i dati anatomici di fusto e foglia in un modello idraulico per stimare la distribuzione delle resistenze lungo il percorso idraulico per valutare in che modo l'anatomia del sistema di trasporto influisca sulla fisiologia dell'intero albero (Studio 4).
Questa tesi ha evidenziato che la lunghezza del percorso (vale a dire l'altezza della pianta e le dimensioni della foglia) è il fattore principale che influenza l'architettura idraulica dell'albero. La dimensione del condotto sia nel fusto che nella foglia è determinata dalla distanza dalle parti terminali, rispettivamente l'apice del fusto o la punta della foglia. Le condizioni climatiche risultano avere un effetto marginale (non significativo) sui tratti anatomici del fusto e nella foglia, le dimensioni dei condotti dello xilema sono statisticamente indipendenti rispetto alle variazioni nelle dimensioni della pianta. Questa rigida architettura idraulica dell'albero, dal fusto alla foglia, consente di minimizzare l'effetto della lunghezza del percorso sulla resistenza idraulica, confinando quasi l'intero gradiente del potenziale idrico all'interno delle foglie.
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Ocheltree, Troy W. "Growth and survival during drought: the link between hydraulic architecture and drought tolerance in grasses." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/13803.
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Doctor of Philosophy<br>Department of Agronomy<br>P.V. Vara Prasad<br>The pathway for the movement of water through plants, from the soil matrix to the atmosphere, constitutes the hydraulic architecture of a plant. The linkage between the hydraulic architecture of woody plants and drought tolerance has received considerable attention, but much less work has been done on grasses. I investigated the linkage between the hydraulic architecture of grasses to physiological patterns of water use across a range of species and conditions. The rate of stomatal conductance (g[subscript]s) and photosynthesis (A) increased acropetally along the leaves of 5 grass species, which is a unique feature of this growth form. The internal structure of leaves also changed acropetally in order to minimize the pressure gradient across the mesophyll that would otherwise occur as a result of increasing g[subscript]s. The resistance to water movement through the mesophyll represented 80-90% of leaf resistance in six genotypes of Sorghum bicolor L. (Moench). This resistance was most important in controlling g[subscript]s and A when water was readily available, but as soil-moisture decreased it was the efficient transport of water through the xylem that was most important in maintaining plant function. I also investigated the relationship between hydraulic architecture and stomatal responses of grasses to increasing Vapor Pressure Deficit (D). Grasses with a larger proportion of their hydraulic resistance within the xylem were less sensitive to increasing D and plants with high root conductance maintained higher rates of gas exchange D increased. Finally, I investigated the tolerance of grasses to extreme drought events to test if there was a trade-off between drought tolerance and growth in grasses. Plants with drought tolerant leaf traits typically sacrificed the ability to move water efficiently through their leaves. Having drought tolerant leaves did not limit the plants ability to have high rates of gas exchange, and, in fact, the most drought tolerant plants had the high rates of g[subscript]s when expressed on a mass basis. Leaf-level drought tolerance did contribute to species’ occurrence, as the drought intolerant species I studied are not commonly found in low precipitation systems. The results presented here highlight the importance of studying the hydraulic architecture of plants to provide a better understanding of what controls plant function across a range of environmental conditions.
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Palacios, Jonathan, Erik Maquera, and Carlos Toledo. "Hydraulic Technology, Agricultural Expansion, And Non-Monumental Settlements During The Lima Period." Pontificia Universidad Católica del Perú, 2016. http://repositorio.pucp.edu.pe/index/handle/123456789/113331.
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The purpose of this article is to provide new evidence that contributes to an understanding of the processes that led to the creation of Late Lima monumental centers. is evidence comes from the Huachipa plains and non-monumental settlements located in the middle Rimac Valley such as San Antonio-Huachipa, El Golf de Huampaní (also known as El Vallecito), and Pancha Paula located in the Chillon valley.<br>El propósito de este trabajo es aportar nueva evidencia que contribuya a explicar los procesos que dieron origen a los centros monumentales Lima Tardío, con evidencia procedente de la llanura de Huachipa y asentamientos no monumentalesdel valle medio del Rímac como San Antonio-Huachipa, El Golf de Huampaní (en adelante El Vallecito) y Pancha Paula en el valle del Chillón.
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Azolibe, Ifeanyi. "Architecture of a cyber-physical system for aircraft fuel control systems tests." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/8503/.
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The aircraft fuel control system makes sure an engine has the precise amount of fuel required to generate power and thrust for every stage of flight. It therefore plays a role in determining the economics of flight. In order to maintain the economic equilibrium of performance and flight safety, it undergoes a Maintenance Repair or Overhaul (MRO) service after several hours of operation. A critical aspect of the MRO service is the test performed to validate the airworthiness of a fuel control system before it returns to service. The test of aircraft fuel control systems is human-centric by design. The operator uses a network of test systems to generate in-flight conditions similar to what the Unit-Under-Test (UUT) experiences on-board an aircraft engine, then performs tests to validate and verify its airworthiness. Thereafter, test results are recorded for regulatory compliance reasons after each test is performed successfully. An analysis of the test specification for the UUT involved in this study revealed 90% of an operator’s touch-time is automatable. The functions of control, data processing, data entry and supervision must be achieved automatically if they are to be performed autonomously by a cyber-physical test system. But the automation of these activities at the micro level does not guarantee their autonomous execution at a macro level by such a cyber-physical system composed of the network of test systems. Therefore, knowledge of a multidisciplinary array of fundamental concepts and how they can be fused to execute the test of aircraft fuel control systems autonomously, have been developed as presented in this thesis. For the function of process control, the response of the processes used to set test conditions is ~ 50Hz, five times the rate of process responses reported in typical process industries where automation of process control have been achieved. As a result of this fundamental knowledge, the design of the architectures for the functions of control and data processing is an asynchronous one. Noting that none of the data is fed back through a network like the case of Networked Control Systems or Supervisory Control and Data Acquisition Systems. The realization of the control functions for each process used to set test conditions is based on control laws synthesized through modelling of their respective actuation mechanisms. Of the three models developed, a 2nd order model has been identified as been representative of the dynamic and steady-state characteristics of each actuation mechanism. A typical actuation mechanism contains a high number of masses and springs whose physical modelling resulted in a model of 12th order. This model is highly unrepresentative of the transient and steady-state response observed in the process due to difficulty in estimating the internal parameters of respective actuators. A linear model synthesized from the calibration data of each actuation mechanism has also been investigated and found to be too ideal. Its response is unrepresentative of the dynamic characteristics of the actuation mechanisms. The processes used to generate test conditions have been set simultaneously using a network of PID controllers. The controllers’ gains are an order of ten less than what they were for the sequential set up of test conditions due the fact that there are interactions between the processes inside a UUT. Fundamentally however, this Thesis demonstrates an asynchronous architecture for the control function, which enables a pseudo steady-state execution of tests. In-practice, this has the potential to reduce the time it takes to perform a test by one-third. The function of supervision has been developed in the form of a Fault Detection Isolation and Recovery capability within the cyber-physical test system. The architecture for this function is designed based on minimalizing the constraint of the period of recoverability (PoR), where the deviations from normal operation need to be detected, the outcomes they could result to—diagnosed and recovery strategies executed to prevent test systems or the UUT deviate from normal operation, using measurements acquired in a time < PoR. Oscillations and offsets have been identified as the major causes of deviations in subsystems during the test of the aircraft fuel control system in this study. In order to diagnose a deviation, a fuzzy inference engine has been developed over a Fault Tree Analysis approach because it makes the automation of domain knowledge needed to realize the supervision function effective. Nevertheless, the contributions of this thesis are the knowledge gaps it uncovers and the formalized approaches it proposes in the form of architectures to plug these gaps. It provides a direction on how to actualize not only the concept of automation, but the realization of a cyber-physical system to test an aircraft fuel control systems. It is the architecture of a singular system capable of executing the functions performed by an operator autonomously, and surpassing what can be achieved in the case of simultaneous process control, automated detection and isolation of a critical deviations under the period of recoverability, that is the fundamental contribution of this thesis. So that in the not so distant future the test of aircraft fuel control systems can be performed by machines.
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Dias, Arildo de Souza 1979. "Atributos foliares e anatômicos do xilema em espécies de árvores e lianas da Floresta Atlântica." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314996.
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Orientadores: Fernando Roberto Martins, Rafael Silva Oliveira<br>Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia<br>Made available in DSpace on 2018-08-22T21:00:03Z (GMT). No. of bitstreams: 1
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Previous issue date: 2013<br>Resumo: Compreender como espécies de plantas diferenciam-se em relação a atributos funcionais para aquisição e utilização de recursos, e se a relação entre esses atributos varia em função de diferenças ambientais, como pluviosidade total e sazonalidade, e uma forma de construir uma ecologia mais preditiva no contexto das mudanças climáticas globais. Nesta tese investigamos como arvores e lianas se diferenciam em relação a atributos funcionais da folha dos ramos. Analisamos-nos se o relacionamento entre esses atributos diferia considerando a variação de pluviosidade e sazonalidade de duas fitofiosionomias da Floresta Atlântica, a floresta ombrofila densa (FO) e a floresta estacional semedicidua (FS). Encontramos diferenças não são na amplitude, mas também na forca do relacionamento entre os atributos funcionais foliares estudados. Essas diferenças parecem ser determinadas pela diferença ambiental entre as duas florestas estudadas e por características intrínsecas do habito de crescimento de lianas e arvores. A anatomia do xilema das espécies de lianas e arvores da FO difere em relação à das espécies da FS, mesmo quando consideramos o parentesco filogenético. Por investir pouco em tecidos de sustentação esperava-se menor conteúdo de lignina nos ramos de lianas, entretanto nosso resulto foi o oposto. Encontramos a razão S/G dos monômeros syringil e guaiacil que compõe a lignina menor que um para duas espécies de lianas. Indicando que ha maior deposição de lignina em vasos de xilema do que em fibras. Esse fato pode estar relacionado à maior eficiência em condutividade hidráulica de lianas ou a requerimentos biomecânicos específicos dos ramos de lianas. Em particular, ressalta-se o fato de que lianas foram mais eficientes em captar luz (menor MFA) e tiveram maior condutividade hidráulica potencial (Kp) do que arvores na FS. A maior competitividade de lianas frente arvores apenas na FS tem implicação importante no cenário de mudanças climáticas<br>Abstract: Understanding how plant species differentiated in functional traits for resources acquisition and use, and if the relationships among those traits vary in according with environmental characteristics such as rainfall and seasonality, could lead to a more predictive science in the context of global change. Here we investigate how trees and lianas differ in leaf and xylem anatomical traits related to water transport and hydraulic architecture. We analyze the relationships among those traits taking into account the variation in rainfall and seasonality between two types of Atlantic Forest, semediciduous seasonal forest (SF) and the dense ombrophilous forest (OF). We found differences not only in range, but in the strength of the relationship among leaf functional traits, which in turn could be related to environmental differences between the two forests studied. The xylem anatomy of lianas and tree species of OF differ compared to species of SF despite taking to account the phylogenetic relatedness. Since lianas have low investment in support tissues we expected lower lignin content in the branches of lianas. However, we found the opposite pattern. Another unexpected result found for two liana species was the ratio to the monomers syringyl and guayacil present at lignin (S/G) lower than one. This result indicates that there is more deposition of lignin in xylem vessel walls than fibers, what in turn would be linked to greater efficiency in hydraulic conductivity of lianas or to specific biomechanical requirements of the branches of lianas. In particular, we highlighted the fact that liana species are more efficient in light acquisition (lower LMA) and had higher hydraulic conductivity (Kp) relative to trees just in the SF. These lianas competitive advantages over trees have important implications in the context of climatic changes<br>Doutorado<br>Biologia Vegetal<br>Doutor em Biologia Vegetal
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Marras, Francesco. "Gestione dell’acqua e gestione della terra : nuovi approcci di progetto per il paesaggio rurale della Sardegna." Thesis, Toulouse 2, 2017. http://www.theses.fr/2017TOU20025/document.
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Ce travail de recherche est résultat d’une collaboration active entre les deux écoles d’architecture de Toulouse et le DICAAR de Cagliari qui explore la relation entre le paysage rural et le projet d’architecture. La choix d’une thèse qui se focalise sur le cas d’étude “local” se détache de la dimension de l’individu particulier, encarré comme cas typique de la Méditerranée, espace de condensation de nouvelles dynamiques agricoles liées au déplacement d’intérêt de la ville au village, avec les changements climatiques et ses influences sur l’architecture et les cultures constructives locales. La Sardaigne est un cas de recherche intéressant, soit pour la variété de son territoire, soit pour les changements climatiques qui voient une radicalisation progressive des conditions de l’intermittence de l’eau. La lecture des principes traditionnels de gestion de l’eau devient la base pour définir les instructions du projet qui doit comprendre la prévention des risques et la production de nouveaux espaces pour la campagne grâce à des techniques de gestion de l’eau. Les cas choisis sont situés sur les quatre rivières les plus importantes de la Sardaigne, qui ont été soumis à des phénomènes météorologiques extrêmes. Les projets sont basés sur la notion de temps, en particulier de la réversibilité de l’intervention, et de la définition de dispositifs légers. Dans la dernière section on résume une matrice des bonnes pratiques et des lignes directrices pour la gestion de l’eau et la gestion des terres qui est basée sur l’identification et l’analyse des questions critiques, le projet d’action qui utilise les technologies et la définition des espaces de qualité. Le projet doit se baser sur un concept de développement durable qui regarde une architecture qui se auto-soutiens, un projet de paysage qui peut produire par soi-même les ressources nécessaires<br>This research is the result of an active collaboration between the two schools of architecture of Toulouse and the DICAAR of Cagliari, which explores the relationship between the rural landscape and the project. The research deals with architecture design in weak contexts, exploring the possibilities offered by water techniques in rural areas. The field survey is Sardinia, characterized by a difficult relationship with water, caused by intermittence that generates problems like drought and flooding. It is necessary to understand the rules of water and land management in order to develop a new operational line on the territory. Reflecting on traditional techniques in terms of standards intends to understand the primary management rules to be applied in the contemporary project, the construction details of the scale, but also on thescale of the urban network and territory, useful for the identification, prevention and management of risks. Reading the principles of management becomes the basis for defining project instructions which must include risk prevention and the production of new areas for the campaign through water management techniques. Selected case studies are located on the four most important rivers of Sardinia, which have historically been subjected to extreme weather events. The projects are based on the notion of time, in particular the reversibility of the intervention, with the construction of an abacus of good practices and new architectures based on the identification and analysis of critical issues, the action project that usestechnologies and the definition of quality spaces. The matrix reflects on a series of projects that addressed the relationship between technology and landscape in complex climatic conditions. The project must be based on a concept of sustainable development that looks at a self-supporting architecture, a landscape project that can produce by itself the resources
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Jalais, Savitri. "Développement des ghâts à Bénarès : dispositif architectural et espace urbain." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1054.
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L'image de la ville de Bénarès (Kāśī, Varanasi) est liée à son ensemble de ghāṭ – berges en forme de gradins – qui se déploie de façon monumentale sur la rive concave d'un méandre du Gange. L'aménagement de ce front d'eau s'inscrit dans un contexte culturel particulier qui nécessite un rapport de proximité avec l'eau du fleuve. La construction et le développement de ce front d'eau dans le temps et la manière composite dont les éléments architecturaux s'y sont intégrés, interrogent aujourd'hui cette grande unité urbaine qui forme un espace public de plus de 6 km de long. L'objectif de cette thèse est de comprendre les éléments qui ont concouru à la naissance et au développement de ce front. La forme architecturale et urbaine du ghāṭ est considérée comme un dispositif construit modulable adapté à un milieu fluvial, à une topographie et à des pratiques liées à la culture du lieu, qui facilite l'accès à l'eau quel que soit son niveau. M'appuyant sur des images anciennes, sur une série d'enquêtes de terrain et de relevés architecturaux, ainsi que sur des plans de travaux officiels, j'étudie les techniques de construction face aux contraintes de l'eau, j'observe et j'analyse le dialogue de cette forme de berge avec la géographie et le paysage urbain pour en mieux approcher son architecture et j'explique la matérialisation du ghāṭ par les pratiques diverses qui s'y déploient et les parcours symboliques qui y font référence. La relation toute particulière que la ville entretient avec son fleuve par l'architecture des ghāṭ explique son potentiel urbanistique inhérent à son développement dans le temps et le long de la berge<br>The image of Benares (Kāśī, Varanasi) is closely associated to the architecture of its riverfront composed of ghats – steps and terraces – that stretch out in a monumental way on the concave bank of a meander formed by the river Ganges. The expansion of this riverfront has to be understood in relation to a cultural tradition that demands a close proximity to the waters of the river. The construction and development of this riverfront in time and the various ways in which each architectural element is integrated with the river bank, calls into question its impressive urban unity that forms a public space extending more than 6 km. The aim of this thesis is to identify the elements that have contributed to the origin and the development of this front. The architectural and urban form of the ghat is considered as a constructed flexible device adapted to a specific river environment, a characteristic topography and to practices linked to the culture of the place, which allows for easy access to the varying levels of the river's water level. Based on pictorial archives, interviews, measure drawings done on site and on official planners' drawings, I examine the techniques of hydraulic constructions best adapted to counter the river's currents, I observe and analyze the relations between the riverbank, the geography and the urban landscape so as to better approach the ghats' architecture and I explain the materialization of the ghat through the diverse practices and the symbolic trajectories that surround it. The particular relation that the city entertains with its river, through the architecture of ghats, explains its urban potential inherent to its development in time and space i.e. along its river bank
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Bleby, Timothy Michael. "Water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on mine rehabilitation sites in the jarrah forest of south-western Australia." University of Western Australia. School of Plant Biology, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0004.
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[Truncated abstract. Please see the pdf format for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version for an accurate reproduction.] This thesis examines the water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on bauxite mine rehabilitation sites in the jarrah forest of south-western Australia. The principal objective was to characterise the key environment and plant-based influences on tree water use, and to better understand the dynamics of water use over a range of spatial and temporal scales in this drought-prone ecosystem. A novel sap flow measurement system (based on the use of the heat pulse method) was developed so that a large number of trees could be monitored concurrently in the field. A validation experiment using potted jarrah saplings showed that rates of sap flow (transpiration) obtained using this system agreed with those obtained gravimetrically. Notably, diurnal patterns of transpiration were measured accurately and with precision using the newly developed heat ratio method. Field studies showed that water stress and water use by jarrah saplings on rehabilitation sites were strongly seasonal: being greatest in summer when it was warm and dry, and least in winter when it was cool and wet. At different times, water use was influenced by soil water availability, vapour pressure deficit (VPD) and plant hydraulic conductance. In some areas, there was evidence of a rapid decline in transpiration in response to dry soil conditions. At the end of summer, most saplings on rehabilitation sites were not water stressed, whereas water status in the forest was poor for small saplings but improved with increasing size. It has been recognised that mature jarrah trees avoid drought by having deep root systems, however, it appears that saplings on rehabilitation sites may have not yet developed functional deep roots, and as such, they may be heavily reliant on moisture stored in surface soil horizons. Simple predictive models of tree water use revealed that stand water use was 74 % of annual rainfall at a high density (leaf area index, LAI = 3.1), high rainfall (1200 mm yr-1) site, and 12 % of rainfall at a low density (LAI = 0.4), low rainfall (600 mm yr-1) site, and that water use increased with stand growth. A controlled field experiment confirmed that: (1) sapling transpiration was restricted as root-zone water availability declined, irrespective of VPD; (2) transpiration was correlated with VPD when water was abundant; and (3) transpiration was limited by soil-to-leaf hydraulic conductance when water was abundant and VPD was high (> 2 kPa). Specifically, transpiration was regulated by stomatal conductance. Large stomatal apertures could sustain high transpiration rates, but stomata were sensitive to hydraulic perturbations caused by soil water deficits and/or high evaporative demand. No other physiological mechanisms conferred immediate resistance to drought. Empirical observations were agreeably linked with a current theory suggesting that stomata regulate transpiration and plant water potential in order to prevent hydraulic dysfunction following a reduction in soil-to-leaf hydraulic conductance. Moreover, it was clear that plant hydraulic capacity determined the pattern and extent of stomatal regulation. Differences in hydraulic capacity across a gradient in water availability were a reflection of differences in root-to-leaf hydraulic conductance, and were possibly related to differences in xylem structure. Saplings on rehabilitation sites had greater hydraulic conductance (by 50 %) and greater leaf-specific rates of transpiration at the high rainfall site (1.5 kg m-2 day1) than at the low rainfall site (0.8 kg m-2 day1) under near optimal conditions. Also, rehabilitation-grown saplings had significantly greater leaf area, leaf area to sapwood area ratios and hydraulic conductance (by 30-50 %) compared to forest-grown saplings, a strong indication that soils in rehabilitation sites contained more water than soils in the forest. Results suggested that: (1) the hydraulic structure and function of saplings growing under the same climatic conditions was determined by soil water availability; (2) drought reduced stomatal conductance and transpiration by reducing whole-tree hydraulic conductance; and (3) saplings growing on open rehabilitation sites utilised more abundant water, light and nutrients than saplings growing in the forest understorey. These findings support a paradigm that trees evolve hydraulic equipment and physiological characteristics suited to the most efficient use of water from a particular spatial and temporal niche in the soil environment.
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Cunningham, Andrew Donald. "Monte Carlo simulation in the marine environment." Thesis, Liverpool John Moores University, 2011. http://researchonline.ljmu.ac.uk/6001/.
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Franks, D. A. "An investigation into the application of formal decision making techniques to design Alterations and Additions (As&As) for vessels of the Royal Fleet Auxiliary (RFA)." Thesis, Liverpool John Moores University, 2018. http://researchonline.ljmu.ac.uk/8749/.
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The Royal Fleet Auxiliary (RFA) is a flotilla of ships, owned by the United Kingdom (UK) Ministry of Defence (MoD), which serves to resupply naval vessels during worldwide operations. Design Alterations and Additions (As&As) are implemented throughout their service lives in order to ‘Upgrade’ and ‘Update’ their capability. This research offers an original contribution to knowledge by applying formal decision making techniques to A&A reasoning in a way that, to the best knowledge of the researcher, has not previously been implemented as an integral part of the in-service design control process for RFA ships. In delivering this contribution, Multi Attribute Decision Making (MADM) techniques are investigated and applied. Three MADM techniques are applied: SAW (Simple Additive Weighting), AHP (Analytic Hierarchy Processes) and TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution). Application of these techniques defines the scope boundary and so rules out exhaustive investigation into the wider decision making approaches that could form the focus of future research. Literature reviews indicate that formal decision techniques have been extensively studied and applied – seemingly to the point of saturation. For this reason, the research does not claim to have developed new techniques. Rather, the contribution to knowledge lies in the systematic application of the techniques. In this respect, a niche topic is identified involving the implementation of As&As during Fleet Time (FT). Investigation results in the systematic identification and categorisation of the Risk Factors (RFs) constraining FT implementation. Two different techniques (SAW and AHP) are applied to FT As&As. The outcomes demonstrate a consistent trend and so offer mutual assurance. In addition, comparison of the techniques indicates that, whilst SAW offers a convenient and intuitive approach, the AHP imposes a higher cognitive burden. This is regarded as significant by the researcher since As&As are subject to schedule and cost constraints, whereby pragmatic and proportional approaches are more likely to find programme acceptance. Based upon an actual decision involving the selection of materials for a ship sea water system, TOPSIS is used to evaluate the options against key criteria. A sensitivity analysis indicates that selection will be influenced in the direction of the criteria weighting. Since ‘procurement cost’ is an important criterion for As&As, the thesis demonstrates a methodology for the delivery of robust cost estimates. This involves the treatment of cost uncertainty using risk analysis software based upon the Monte Carlo technique. The researcher consolidates studies into systematic decision methodologies for As&As. Credibility is claimed since methodologies are based upon established techniques and tested against A&A examples. Credibility is also claimed from the theme, running throughout the thesis, that the studies build upon the professional experience of the researcher and involve engagement with Suitably Qualified and Experienced Personnel (SQEP).
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Zhang, Xi. "Multi-model method for simulating 2D surface-piercing wave-structure interactions." Thesis, City, University of London, 2018. http://openaccess.city.ac.uk/19772/.
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Wave-structure interactions play an important role on the design and maintenance of coastal and offshore constructions. Computational Fluid Dynamics (CFD) is a convenient tool for analyzing wave-structure interactions in costal and offshore engineering. The potential model and the viscous model are traditional mathematical models for wave-structure interactions, which have disadvantages in computational robustness, when they are applied individually. Therefore, recently, more and more multi-model methods are used for coupling the viscous model and the potential model together. So far, in the existing multi-model methods, the surface-piercing structure only exists in the viscous domain so that the viscous domain should be large enough. In order to improve the computational efficiency, some multi-model methods are developed, where the structure is considered in both viscous domain and Euler domain. Firstly, by function-decomposition method, an Euler-viscous hybrid model is proposed. Comparing with the other function-decomposition hybrid models, a surface-piercing structure exists in both a large Euler domain and a small viscous domain. By this, the reflection, diffraction, and radiation waves from the structure can be considered in both two computational domains. Therefore, the computational efficiency can be enhanced remarkably. To couple the Euler model and the viscous model, complementary RANS equations are deduced, with complementary turbulence models. Corresponding boundary conditions are also developed for coupling. A relaxed scheme is proposed for damping the viscous effects and keeping free surface consistent. For wave interactions with moving structures, the transition of total forces acting on the structure from the viscous domain to the Euler domain is used to guarantee the same motion of structures in two domains. Secondly, the function-decomposition Euler-viscous hybrid model is extended by domain-decomposition method. Then, function-decomposition method and domain-decomposition method are coupled together. The wave generation and propagation is solved in a potential domain. By this, the computational efficiency for wave-structure interactions in a large real wave tank can be improved. Computational robustness of Euler-viscous hybrid model for surface-piercing wave-structure interactions are studied by some cases. It is found that the size of the viscous domain, the length of transition zone, and mesh resolution can affect computational precision. Computational efficiency is mainly affected by the size of the viscous domain. For extended Euler-viscous hybrid model, the distance before reaching the inlet boundary of the Euler domain plays a crucial role on computational accuracy and efficiency. Validations are done by comparing numerical results based on hybrid models, conventional RANS model and experimental results. It is shown that hybrid models own the same computational accuracy as the conventional RANS model. Furthermore, the computational accuracy can be improved remarkably. In some cases, more than 85% CPU time can be saved. The hybrid models are applied to simulate wave interactions with a structure subjected to seabed effects. By comparing with numerical simulations based on the conventional RANS model, it is indicated that hybrid models can be also used on complex computational domain. Some properties of wave interactions with a floating structure subjected to a submerged structure are found by numerical simulations.
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de, Ruyter Marcus J. M. "Two-dimensional cut plan optimization for cutter suction dredgers." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/79367/.
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Optimal cut plans for cutter suction dredgers aim to maximize operational efficiency. Maximizing operational efficiency involves minimization of stoppage time resulting from non-productive dredger movements. To automate a systematic search for optimal twodimensional cut plans for cutter suction dredgers two models with an adaptive simulated annealing-based solution approach were developed. The first model, the dredge cut nesting model, optimizes irregular stock cutting problems where stencils represent dredge cuts and sheets represent dredging areas. Stencils are collections of unit dredge cuts with dimensions related to an effective cutting width which can be achieved with the cutter suction dredger considered. The objectives of the dredge cut nesting model are to maximize sheet coverage and to minimize stencil overlap. Centroids of unit dredge cuts of final nest layouts are extracted and used as grid nodes in the second model. The second model, the dredger routing model, optimizes asymmetric travelling salesperson problems with turning costs. The objectives of the dredger routing model are to minimize total route length and sum of turning angles, and to maximize average link length. A link consists of two or more route edges which are aligned with each other to within specified limits. A significant result of this research is that an engineering application of both models showed that two-dimensional cut plans for cutter suction dredgers can be systematically optimized and that dredger routes with minimum turning costs can be found. However, results also showed that the dredger routing model is not yet sophisticated enough to find cut plans for cutter suction dredgers for which overall project execution time is minimal.
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Chenlemuge, Tselmeg [Verfasser], Markus [Akademischer Betreuer] Hauck, Christoph [Akademischer Betreuer] Leuschner, and Dirk [Akademischer Betreuer] Gansert. "Drought Adaptation of the Fine Root System and Hydraulic Architecture of Larix sibirica at its Southern Distribution Limit General introduction / Tselmeg Chenlemuge. Gutachter: Markus Hauck ; Christoph Leuschner ; Dirk Gansert. Betreuer: Markus Hauck." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1065044720/34.
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Soulet, Quentin. "Typologie, architecture et évolution des systèmes silicoclastiques des marges abruptes. Analyse comparée de la marge Ligure au Plio-Quaternaire et de la marge San-Pedro au Crétacé supérieur." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066694/document.
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Les systèmes sédimentaires turbiditiques présentent un double intérêt académique et industriel puisqu’ils constituent à la fois des archives des conditions environnementales et des réservoirs pétroliers potentiels. Parmi les nombreux paramètres contrôlant l’organisation sédimentaire de ces systèmes l’inclinaison de la pente continentale apparait être un paramètre majeur. L’analyse de l’influence de l’inclinaison de la pente et de ces variations sur l’hydrodynamique des écoulements sédimentaires et ainsi sur l’architecture des systèmes turbiditiques revêt un caractère crucial tant du point de vue académique que pétrolier. Ce travail s’appuie sur l’analyse haute résolution de données acoustiques (bathymétrie, imagerie multifaisceaux, sismique THR, sonar latéral) acquises sur la marge abrupte du Golfe de Gênes (Malisar, Fables, Prisme, Gelo) et de l’analyse d’un bloc de sismique 3D sur la marge abrupte Ivoirienne. Les accumulations turbiditiques des deux sites témoignent de processus de ségrégation des particules avec le piégeage des particules les plus grossières dans des structures en plunge pools, cyclic steps ou slope break deposits. L’étude fine de ces corps liés au ressaut hydraulique apporte ici un éclairage inédit sur la continuité des corps sableux à la transition canyon/lobe et permet ainsi de proposer un nouveau scénario de modèle réservoir. De plus l’analyse de ces deux zones d’études met en évidence l’impact direct de l’activité tectonique sur l’architecture des accumulations turbiditiques par la mise en place et le maintien d’une zone de rupture de pente où le phénomène de ressaut hydraulique peut perdurer au cours du temps<br>Turbidite systems present both academic and industrial interests since they are archives of environmental conditions and potential oil reservoirs. Among many parameters controlling the sedimentary organization, the continental slope inclination appears to be a major parameter. The analysis of slope inclination’s and these variations on the hydrodynamic of sedimentary flows and thus on turbidite systems architecture is a crucial character for both academic and industrial interests. The Pliocene-Quaternary turbidite systems of the Gulf of Genoa and upper margin of the Ivorian Cretaceous develop on margins with steep slope profiles controlled by tectonic processes and are suitable and complementary items for the Study of turbidite sedimentation in context of abrupt margin. This work is based on the high-resolution analysis of acoustic data (bathymetry, multibeam imaging, seismic THR, sidescan sonar) acquired on the steep margin of the Gulf of Genova (Malisar, Fables, Prism, Gelo) and the analysis of a 3D seismic block on the Ivorian steep margin. Turbidite accumulations of two sites demonstrate particle segregation processes with trapping coarser particles into specific structures such as plunge pools and cyclic steps. The detailed study of these bodies related to hydraulic jump sheds a new light on the continuity of sand bodies in the transition canyon / lobe and allows the designing of a new reservoir model scenario. Further analysis of these two areas of study shows the direct impact of tectonic activity on the architecture of turbidite accumulations by establishing and maintaining a nick area where the phenomenon of hydraulic jump can be maintained over time
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Khansaritoreh, Elmira [Verfasser], Markus [Akademischer Betreuer] Hauck, Edmone [Gutachter] Roffael, and Christoph [Gutachter] Leuschner. "Effects of Land Use, Habitat Fragmentation and Climate Warming on Stem Increment, Regeneration, and Hydraulic Architecture of Larix sibirica in the Mongolian Forest-Steppe / Elmira Khansaritoreh ; Gutachter: Edmone Roffael, Christoph Leuschner ; Betreuer: Markus Hauck." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://d-nb.info/1159768870/34.
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Soulet, Quentin. "Typologie, architecture et évolution des systèmes silicoclastiques des marges abruptes. Analyse comparée de la marge Ligure au Plio-Quaternaire et de la marge San-Pedro au Crétacé supérieur." Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066694.
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Les systèmes sédimentaires turbiditiques présentent un double intérêt académique et industriel puisqu’ils constituent à la fois des archives des conditions environnementales et des réservoirs pétroliers potentiels. Parmi les nombreux paramètres contrôlant l’organisation sédimentaire de ces systèmes l’inclinaison de la pente continentale apparait être un paramètre majeur. L’analyse de l’influence de l’inclinaison de la pente et de ces variations sur l’hydrodynamique des écoulements sédimentaires et ainsi sur l’architecture des systèmes turbiditiques revêt un caractère crucial tant du point de vue académique que pétrolier. Ce travail s’appuie sur l’analyse haute résolution de données acoustiques (bathymétrie, imagerie multifaisceaux, sismique THR, sonar latéral) acquises sur la marge abrupte du Golfe de Gênes (Malisar, Fables, Prisme, Gelo) et de l’analyse d’un bloc de sismique 3D sur la marge abrupte Ivoirienne. Les accumulations turbiditiques des deux sites témoignent de processus de ségrégation des particules avec le piégeage des particules les plus grossières dans des structures en plunge pools, cyclic steps ou slope break deposits. L’étude fine de ces corps liés au ressaut hydraulique apporte ici un éclairage inédit sur la continuité des corps sableux à la transition canyon/lobe et permet ainsi de proposer un nouveau scénario de modèle réservoir. De plus l’analyse de ces deux zones d’études met en évidence l’impact direct de l’activité tectonique sur l’architecture des accumulations turbiditiques par la mise en place et le maintien d’une zone de rupture de pente où le phénomène de ressaut hydraulique peut perdurer au cours du temps<br>Turbidite systems present both academic and industrial interests since they are archives of environmental conditions and potential oil reservoirs. Among many parameters controlling the sedimentary organization, the continental slope inclination appears to be a major parameter. The analysis of slope inclination’s and these variations on the hydrodynamic of sedimentary flows and thus on turbidite systems architecture is a crucial character for both academic and industrial interests. The Pliocene-Quaternary turbidite systems of the Gulf of Genoa and upper margin of the Ivorian Cretaceous develop on margins with steep slope profiles controlled by tectonic processes and are suitable and complementary items for the Study of turbidite sedimentation in context of abrupt margin. This work is based on the high-resolution analysis of acoustic data (bathymetry, multibeam imaging, seismic THR, sidescan sonar) acquired on the steep margin of the Gulf of Genova (Malisar, Fables, Prism, Gelo) and the analysis of a 3D seismic block on the Ivorian steep margin. Turbidite accumulations of two sites demonstrate particle segregation processes with trapping coarser particles into specific structures such as plunge pools and cyclic steps. The detailed study of these bodies related to hydraulic jump sheds a new light on the continuity of sand bodies in the transition canyon / lobe and allows the designing of a new reservoir model scenario. Further analysis of these two areas of study shows the direct impact of tectonic activity on the architecture of turbidite accumulations by establishing and maintaining a nick area where the phenomenon of hydraulic jump can be maintained over time
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Link, Roman Mathias [Verfasser], Christoph [Akademischer Betreuer] Leuschner, Christoph [Gutachter] Leuschner, et al. "The role of tree height and wood density for the water use, productivity and hydraulic architecture of tropical trees / Roman Mathias Link ; Gutachter: Christoph Leuschner, Bernhard Schuldt, Holger Kreft, Hermann Behling, Dirk Hölscher, Erwin Bergmeier ; Betreuer: Christoph Leuschner." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://d-nb.info/1212660773/34.
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Fichot, Régis. "Variabilité structurale et fonctionnelle du xylème et plasticité en réponse à la sécheresse chez le peuplier." Phd thesis, Université d'Orléans, 2010. http://tel.archives-ouvertes.fr/tel-00579446.
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Cette thèse visait à caractériser l'architecture hydraulique du xylème chez les hybrides de peuplier Populusdeltoides × P. nigra et à juger de ses relations avec le fonctionnement hydrique et carboné de l'arbre en conditions d'irrigation contrastées. A cette fin, huit génotypes se distinguant par leur discrimination isotopique vis-à-vis du carbone 13 ont été cultivés en pépinière. Nos travaux ont permis de mettre en évidence d'importantes variations entre génotypes pour les caractéristiques anatomiques du xylème, l'efficience hydraulique de la tige et de la plante entière ainsi que la résistance à la cavitation. Nos travaux démontrent également que l'anatomie et la résistance à la cavitation du xylème s'ajustent aux conditions hydriques du milieu de façon génotype-dépendante. En condition hydrique non limitante, nous avons mis en évidence un compromis entre l'efficience hydraulique et la résistance à la cavitation ou le potentiel de croissance. Ces deux compromis expliquent la relation positive observée entre la résistance à la cavitationet le potentiel de croissance. En condition hydrique limitante, cette relation n'était toutefois plus observable. Aucune relation n'a pu être identifiée entre les propriétés hydrauliques et l'efficience d'utilisation de l'eau. Ces travaux suggèrent que certaines relations couramment observées à l'échelle inter-spécifique ne sont pas nécessairement applicables à des échelles d'étude plus réduites. Ce travail ouvre des perspectives sur le plan fondamental pour l'identification du déterminisme moléculaire à l'origine de la plasticité structurale observée et sur le plan appliqué, pour la création variétale.
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Schmitz, Juliano. "Architecture de la pousse de pommier en réponse à des températures hivernales froides et douces : typologie de la ramification axillaire au printemps et relation avec le statut hydrique du bourgeon pendant l'hiver précédent." Thesis, Montpellier, SupAgro, 2014. http://www.theses.fr/2014NSAM0040/document.
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Le pommier (Malus Xdomestica Borkh.) cultivé en climat à hiver doux, avec un manque d'une quantité suffisante d'heures de températures froides, présente des anomalies morphologiques et physiologiques. Sur le plan de la phénologie, il s'agit notamment d'un débourrement printanier tardif et désynchronisé entre les différents bourgeons d'un même arbre. Sur le plan agronomique, la floraison et la nouaison sont irrégulières et étalées dans le temps et conduisent à une faible production de fruits. L'objectif de ce travail de thèse est premièrement de mieux caractériser les effets des températures hivernales sur le débourrement et la croissance des bourgeons axillaires en distinguant les effets respectifs des températures hivernales et du génotype. Il s'agit ensuite de vérifier l'hypothèse que les effets des températures sur le débourrement du bourgeon s'effectue via les effets sur son statut hydrique. Les travaux ont été réalisés en France et au Brésil. En France, les expérimentations ont porté sur quatre cultivars à fort besoin (‘Granny Smith', ‘Royal Gala', ‘Starkrimson') ou faible besoin (‘Condessa') en froid, cultivés en hiver froid (conditions extérieures) et doux (serres climatisées). Nous montrons que le débourrement résulte d'une séquence d'évènements où la température hivernale joue un rôle primordial sur les mécanismes de sortie de dormance et donc sur le débourrement proprement dit, durant la période froide. Les caractéristiques propres du cultivar jouent par contre un rôle dans la croissance ultérieure des bourgeons et donc dans l'architecture finale de la pousse du pommier. Par ailleurs, la chute tardive des feuilles, caractéristique du pommier en hiver doux, a peu d'effets sur le débourrement et la croissance des bourgeons. L'analyse du statut hydrique des bourgeons a été réalisée sur le tiers distal des pousses de pommier caractérisé par une forte fréquence de ramification en climat à hiver froid. Nous montrons que, dans la période allant de l'endordormance à la phase de pré-débourrement, la conductance hydraulique à la jonction entre l'axe porteur et le bourgeon varie peu au cours de l'hiver et entre cultivars. Par ailleurs, durant cette même période le potentiel hydrique intra-bourgeon reste négatif, entre -4.35 and -2.24 MPa. Enfin, quel que soit le cultivar, nous ne montrons pas de relation entre les températures hivernales, le potentiel hydrique ou la teneur relative en eau des bourgeons, et l'aptitude au débourrement ultérieur. Ces résultats suggèrent que le bourgeon est hydrauliquement isolé de son axe porteur pendant toute la période hivernale jusqu'à quelques jours précédant le débourrement. Les expérimentations au Brésil ont porté sur le cultivar ‘Eva ‘ à faible besoin en froid, cultivés en conditions naturelles d'hiver doux. Il s'agissait de vérifier les effets possibles de la position du bourgeon le long de l'axe porteur sur sa taille et sa teneur relative en eau. Nous montrons que, tout au long de l'hiver, les bourgeons distaux sont caractérisés par une plus grande taille et une teneur relative en eau plus élevée que les bourgeons proximaux avec une forte augmentation de la teneur relative en eau une semaine avant le débourrement printanier. Le débourrement acrotone semble donc résulter d'une évolution rapide du statut hydrique du bourgeon en fin d'écodormance. L'ensemble des résultats acquis en France et au Brésil, sur des cultivars caractérisés par des besoins variables en froid hivernal, indique que l'aptitude au débourrement printanier des bourgeons de pommier est davantage lié à un « effet rameau entier » qu'au statut hydrique proprement dit des bourgeons individuels, tout au moins jusqu'à quelques jours avant le débourrement effectif. La pousse annuelle de pommier apparait donc comme une unité morphologique et physiologique intégrée qui, dans un contexte climatique donné, conditionne le statut hydrique de chaque bourgeon et son aptitude au débourrement<br>The apple tree (Malus Xdomestica Borkh.) presents morphological and physiological anomalies when grown in mild winter climates with insufficient winter chilling to overcome winter dormancy. Symptoms are typically delayed and erratic budburst, entailing desynchronized flowering and fruit-set and poor agronomic performances. This thesis aimed at gaining more insights on the following issues. Firstly, what are the effects of winter temperatures on axillary burdburst and bud outgrowth, and what are the respective effects of winter temperatures and cultivar?, and secondly, is there a link between the temperature-dependent budburst and bud water status? Works were done in France and Brazil. In France, experiments were carried out in controlled conditions on four apple cultivars characterized by either high chilling (‘Granny Smith', ‘Royal Gala', ‘Starkrimson') or low chilling (‘Condessa') requirements and were submitted to outdoor-cold and greenhouse-mild winter temperatures. We showed that the actual shoot architecture and budburst resulted from an ordered sequence of events with a pivotal role of winter temperatures on the dormancy completion of individual lateral buds. Endogenous factors related to the cultivar branching pattern overtook the temperature effect on the lateral bud outgrowth. Furthermore, the delayed senescence and subsequent leaf persistence during winter, characterizing the apple tree in the mild winter temperature conditions, had only a weak effect on the topological distribution of budburst and lateral outgrowth. The analyses of bud water status were done on distal buds only, characterized by high budburst frequency in cold winter conditions. We showed that, from endodormancy to the pre-budburst stage, xylem conductance at the stem-to-bud junction did not show consistent changes across cultivars and winter temperature treatments. Bud water potential had negative values, between -4.35 and -2.24 MPa, depending on cultivars and winter temperature treatments. Moreover, whatever the cultivar, there were no significant trends across dates for the effects of winter temperatures on bud water potential and relative water content without a consistent relationship with actual spring budburst frequency. These results suggested that lateral buds were hydraulically isolated from the parent stem during winter until a few days before budburst. The other set of experiments was carried out in Brazil, under mild winter conditions, on the low chilling apple cultivar ‘Eva'. The objectives were to gain more insights on the effect of the position of the over-wintering lateral bud along the whole-parent shoot on bud size and water content. Results highlighted that distal buds were larger and had a higher water content than proximal buds with a strong increase of water content a week before spring budburst. It was concluded that the acrotonic pattern of budburst was mainly established during ecodormancy. As a whole, we showed that spring budburst seemed more related to a whole-shoot effect than to the water status of the individual bud during winter dormancy. Our study substantiated the importance of the whole shoot as an integrated morphological and physiological unit in driving budburst and further growth
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Alléon, Julien. "Vers une représentation à l'échelle globale du microclimat forestier dans le modèle de surfaces continentales ORCHIDEE." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASJ029.
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Les dynamiques temporelles et spatiales des échanges entre les surfaces continentales et l'atmosphère sont en grande partie contrôlées par la végétation. Dans un contexte de changement climatique, la précision de la modélisation des bilans d'énergie, d'eau et de dioxyde de carbone des écosystèmes dans les modèles de surfaces continentales revêt ainsi d'un double enjeu : elle permet d'améliorer la représentation des échanges entre les surfaces et l'atmosphère et, par conséquent, d'améliorer la fiabilité des modèles de climats ; et elle permet également de comprendre et de quantifier l'impact du changement climatique sur le fonctionnement des écosystèmes végétaux. Dans la majorité des modèles, la structure de la végétation est simplifiée, considérée équivalente à une surface d'épaisseur infinitésimale échangeant de l'eau, de l'énergie et des composés avec l'atmosphère (modèle de type "grosse-feuille"). La dynamique complexe des échanges au sein des écosystèmes végétaux, et particulièrement des forêts, incluant le microclimat intra-canopée, reste très mal ou pas représentée dans les modèles actuels. Ce microclimat joue cependant un rôle important dans la régulation des échanges d'énergie et de masse entre la végétation et l'atmosphère et son évolution dans un contexte de changement climatiques est méconnue. Cette étude présente les premières étapes effectuées dans le modèle ORCHIDEE (composante de surface du modèle de climat de l'IPSL) pour l'étude de ce microclimat intra-canopée à l'échelle globale. La représentation simpliste de type "grosse-feuille" utilisée dans ORCHIDEE est remplacée par un modèle d'échanges d'eau et d'énergie au sein de la canopée (suivant une discrétisation verticale). L'intégration de ce modèle est effectuée en deux étapes. La première s'attache à la représentation du transport de l'eau dans le continuum sol-plante-atmosphère et a pour objectif de contraindre les échanges feuille-atmosphère grâce à l'état hydrique de la végétation. Ce travail s'appuie sur une représentation du potentiel hydrique dans les différents compartiments de la plante (i.e. architecture hydraulique). Cette intégration est étudiées de manière détaillée à l'échelle du site avant une étude d'impact globale. La seconde étape consiste à la mise à jour, la mise à niveau et l'amélioration d'un modèle d'échanges d'eau et d'énergie multi-couches entre la végétation et l'atmosphère précédemment implémenté dans une branche d'ORCHIDEE. L'évaluation de ce modèle est effectuée à l'échelle des sites forestiers en comparaison du modèle d'écosystèmes MuSICA sur une base de données crée à cet effet. La comparaison des gradients de température intra-canopée simulés et observés est très encourageante. Elle a aussi permis d'identifier des pistes pour l'amélioration globale du modèle. Enfin, des perspectives sont discutées pour une utilisation de ces modèles à l'échelle globale et notamment pour simuler l'évolution du microclimat sous une canopée forestière en fonction du changement climatique et des pratiques forestières<br>The temporal and spatial dynamics of exchanges between continental surfaces and the atmosphere are largely controlled by vegetation. In the context of climate change, accurately modeling the energy, water, and carbon dioxide balances of ecosystems in land surface models presents a dual challenge: it improves the representation of exchanges between surfaces and the atmosphere, thereby enhancing the reliability of climate models; and it also helps to understand and quantify the impact of climate change on the functioning of plant ecosystems. In most models, the structure of vegetation is simplified, treated as equivalent to an infinitesimal thickness surface exchanging water, energy, and compounds with the atmosphere (a "big-leaf" model). The complex dynamics of exchanges within plant ecosystems, particularly forests, including the intra-canopy microclimate, remain poorly represented or not represented at all in current models. However, this microclimate plays a crucial role in regulating energy and mass exchanges between vegetation and the atmosphere, and its evolution in the context of climate change is not well understood. This study presents the first steps taken in the ORCHIDEE model (the land surface component of the IPSL climate model) to study this intra-canopy microclimate at a global scale. The simplistic "big-leaf" representation used in ORCHIDEE is replaced by a model of water and energy exchanges within the canopy (following vertical discretization). The integration of this model is carried out in two stages. The first focuses on representing water transport in the soil-plant-atmosphere continuum and aims to constrain leaf-atmosphere exchanges based on the water status of the vegetation. This work relies on a representation of water potential in the different compartments of the plant (i.e., hydraulic architecture). This integration is studied in detail at the site scale before conducting a global impact study. The second step involves updating, upgrading, and improving a multi-layer model of water and energy exchanges between vegetation and the atmosphere previously implemented in a branch of ORCHIDEE. The evaluation of this model is conducted at the scale of forest sites in comparison to the MuSICA ecosystem model based on a database created for this purpose. The comparison of simulated and observed intra-canopy temperature gradients is very encouraging. It has also helped to identify avenues for the overall improvement of the model. Finally, prospects are discussed for using these models at a global scale, particularly to simulate the evolution of microclimate under a forest canopy in relation to climate change and forestry practices
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Yuan, QingHui, and Aaron Jogada. "Architecture, Control and NVH Development of Digital Hydraulics for Off-Highway Vehicle Applications." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-199396.
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Digital hydraulics is one of promising technologies having a huge potential to significantly improve energy efficiency in the fluid power industry. In this paper, we present a digital hydraulics solution for mobile market with a large ammount of energy usage by hydraulic components and systems. Specifically, a novel hydraulic architecture, Multiplex Digital Valve (MDV) system that employs digital valves to meet multiple service pressure/flow requirement in off highway vehicles, is introduced. With MDV being integrated in an execavator, signficant hydraulic power saving have been validated compared to the baseline machine with the negative flow control (NFC) architecture. In addition, considering noise is still a critical hurdle for digital hydraulics to be adoped, we develop several noise reduction methods that have been evaluated in simulation environment and implemented in the above MDV. The sound pressure measured from the retrofitted MDV solution with the NVH treatment in the excavator has been improved signficantly over the untreated system such that it is nearly comparable to the baseline machine. The paper also briefly presents the sound quality study for better understanding of human perception and acceptance to nonconventional sound.
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Richartz, Achim. "State of the art digital on-board-electronics vs. potentially disruptive control architectures for hydraulic valves." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71191.
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Currently discussed trends and new technologies regarding cloud or edge computing imply that even most recent designs and functionalities of digital on-board-control electronics may be outdated and eventually will totally disappear. Additionally, those new technologies attract potential users by promises like new use cases e.g. predictive maintenance or a simplified architecture and reduced installation efforts. On the other hand, automation levels and subsequent requirements are often mixed up or discussed too generally. Nevertheless, what is the rue situation today and in the upcoming years? This paper elaborates the potentials of both approaches – state of the art on-board-control electronics and potentially disruptive control architectures for hydraulic valves in order to take the right decision and reflect the pros and cons for each topology by:
a) Architecture of automation: In Terms of strongly hierarchical or multidimensional connected systems.
b) Requirement of installation: By reflecting the dedicated ecosystems, on levels like plant, machine, subsystems.
c) Maturity of technology: Looking on the user’s perspective.
d) Safety and security: From legal and conformity aspects.
e) Performance needs by specific task: In comparing standard to demanding real life applications.
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Lamare, Nicolas. "Les fontaines monumentales en Afrique romaine." Thesis, Paris 4, 2014. http://www.theses.fr/2014PA040017.
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Cette étude porte sur les fontaines monumentales ou nymphées dans les provinces de l’Afrique du Nord à l’époque romaine, sur une période allant du Ier au IVe siècle ap. J.‑C. Nous avons constitué un catalogue des monuments et un corpus épigraphique, à partir de sources bibliographiques et archéologiques recueillies par un travail de terrain. Après avoir rappelé l’histoire des recherches sur l’hydraulique de l’Afrique antique, nous étudions en détail les aspects techniques et architecturaux des fontaines monumentales. Nous proposons une synthèse sur les techniques de construction et le fonctionnement hydraulique, mais également sur la restitution architecturale et du décor sculpté, à l’aide de sources littéraires et iconographiques. Sans proposer de typologie, nous étudions les fontaines dans leur contexte, au sein de la ville et du réseau hydraulique. Nous mettons ainsi en avant l’insertion des fontaines dans la ville et le lien qu’elles entretiennent avec la mise en place des adductions et les programmes urbanistiques. Ces observations rendent possible une étude de la répartition des fontaines dans l’espace urbain et de son impact, décoratif et fonctionnel. L’étude des inscriptions nous permet de mieux envisager le fonctionnement de l’évergétisme, le comportement de la cité et des notables face à ces édifices. Elle est aussi l’occasion de revenir sur les problèmes de vocabulaire qui impliquent une réflexion sur l’appellation des édifices et leur fonction religieuse<br>This thesis deals with monumental fountains or nymphaea in the Roman North Africa provinces from the 1st to the 4th century CE. We have made up a catalogue of the monuments and inscriptions, composed from bibliographical and archaeological sources compiled on-site. We first sum up the history of research on hydraulics in ancient North Africa and then we study in detail the technical and architectural aspects of monumental fountains. We offer a synthesis on building techniques and hydraulic system as well as architectural and ornamental reconstruction with the help of literary and iconographic sources. Avoiding to establish a typology, we contextualise the fountains both within the city and the hydraulic network. Thus we put forward the insertion of fountains in the city and their link with the founding of a new water supply or town-planning programmes. These observations make possible a study of how the fountains were spread out in the urban space and to what extent it had a decorative and functional impact. By studying inscriptions, we may better understand how euergetism worked, just as the behaviour of cities and notables faced with these monuments. We may also go back to questions of vocabulary which imply to think about the appellation of fountains and their religious function
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Drofelnik, Jernej. "Massively parallel time- and frequency-domain Navier-Stokes Computational Fluid Dynamics analysis of wind turbine and oscillating wing unsteady flows." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8284/.
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Increasing interest in renewable energy sources for electricity production complying with stricter environmental policies has greatly contributed to further optimisation of existing devices and the development of novel renewable energy generation systems. The research and development of these advanced systems is tightly bound to the use of reliable design methods, which enable accurate and efficient design. Reynolds-averaged Navier-Stokes Computational Fluid Dynamics is one of the design methods that may be used to accurately analyse complex flows past current and forthcoming renewable energy fluid machinery such as wind turbines and oscillating wings for marine power generation. The use of this simulation technology offers a deeper insight into the complex flow physics of renewable energy machines than the lower-fidelity methods widely used in industry. The complex flows past these devices, which are characterised by highly unsteady and, often, predominantly periodic behaviour, can significantly affect power production and structural loads. Therefore, such flows need to be accurately predicted. The research work presented in this thesis deals with the development of a novel, accurate, scalable, massively parallel CFD research code COSA for general fluid-based renewable energy applications. The research work also demonstrates the capabilities of newly developed solvers of COSA by investigating complex three-dimensional unsteady periodic flows past oscillating wings and horizontal-axis wind turbines. Oscillating wings for the extraction of energy from an oncoming water or air stream, feature highly unsteady hydrodynamics. The flow past oscillating wings may feature dynamic stall and leading edge vortex shedding, and is significantly three-dimensional due to finite-wing effects. Detailed understanding of these phenomena is essential for maximising the power generation efficiency. Most of the knowledge on oscillating wing hydrodynamics is based on two-dimensional low-Reynolds number computational fluid dynamics studies and experimental testing. However, real installations are expected to feature Reynolds numbers of the order of 1 million and strong finite-wing-induced losses. This research investigates the impact of finite wing effects on the hydrodynamics of a realistic aspect ratio 10 oscillating wing device in a stream with Reynolds number of 1.5 million, for two high-energy extraction operating regimes. The benefits of using endplates in order to reduce finite-wing-induced losses are also analyzed. Three-dimensional time-accurate Reynolds-averaged Navier-Stokes simulations using Menter's shear stress transport turbulence model and a 30-million-cell grid are performed. Detailed comparative hydrodynamic analyses of the finite and infinite wings highlight that the power generation efficiency of the finite wing with sharp tips for the considered high energy-extraction regimes decreases by up to 20 %, whereas the maximum power drop is 15 % at most when using the endplates. Horizontal-axis wind turbines may experience strong unsteady periodic flow regimes, such as those associated with the yawed wind condition. Reynolds-averaged Navier-Stokes CFD has been demonstrated to predict horizontal-axis wind turbine unsteady flows with accuracy suitable for reliable turbine design. The major drawback of conventional Reynolds-averaged Navier-Stokes CFD is its high computational cost. A time-step-independent time-domain simulation of horizontal-axis wind turbine periodic flows requires long runtimes, as several rotor revolutions have to be simulated before the periodic state is achieved. Runtimes can be significantly reduced by using the frequency-domain harmonic balance method for solving the unsteady Reynolds-averaged Navier-Stokes equations. This research has demonstrated that this promising technology can be efficiently used for the analyses of complex three-dimensional horizontal-axis wind turbine periodic flows, and has a vast potential for rapid wind turbine design. The three-dimensional simulations of the periodic flow past the blade of the NREL 5-MW baseline horizontal-axis wind turbine in yawed wind have been selected for the demonstration of the effectiveness of the developed technology. The comparative assessment is based on thorough parametric time-domain and harmonic balance analyses. Presented results highlight that horizontal-axis wind turbine periodic flows can be computed by the harmonic balance solver about fifty times more rapidly than by the conventional time-domain analysis, with accuracy comparable to that of the time-domain solver.
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Makusa, Gregory Paul. "Mechanical properties of stabilized dredged sediments : for sustainable geotechnical structures." Licentiate thesis, Luleå tekniska universitet, Geoteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17437.
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Dredging activities at Ports and Harbors are inevitable for the safe navigation of ships and vessels. Dredged material may range from very fine and contaminated sediments to sand and gravels. While, granular dredged material can be directly utilized in civil engineering applications, fine sediments may require further treatment before use. In geotechnical context, fine sediments are characterized by low shear strength and high compressibility. However, these unfavorable properties do not rule out the suitability of these fine dredged sediments for use in geotechnical construction, such as, road embankment, building foundation or as structural backfill in land reclamation. Mass stabilization solidification provides a comprehensive technology for amending fine sediments at high initial water content, resulting into construction materials of improved strength and reduced compressibility. The ultimate in-situ soil behavior types, stiffness and strength properties of stabilized mass depend on various factors such as binders, mixing equipment, curing temperature, in-situ boundary conditions and mostly important the applied preloading weight during the period of curing. However, despite improved mechanical properties for geotechnical applications, the performance of treated materials becomes susceptible to repeated freeze-thaw cycles. Understanding geotechnical design process, which includes evaluation of material properties, loading condition and selection of appropriate constitutive model, is an important task for settlement and stability analysis of structures founded on stabilized mass. The selection of suitable material model is vital for successful finite element analysis. Nevertheless, among all existing constitutive soil models, none of them can capture all aspects of soil behavior. Therefore, the meaningful and quantifiable predictions of field behaviors are possible only if, undisturbed samples or in-situ tests are used for determination of mechanical properties, and the predictive capacity of selected constitutive model comes from the comparison with field observations In the present research work, utilization of cone penetration test (CPT) data for evaluating the mechanical properties of stabilized dredged sediments for geotechnical design and analysis was presented. A large-scale field test at the Port of Gävle was utilized as a case study, to verify the simulated settlement of preloaded stabilized dredged sediments. The stabilized mass–soil classification behavior type was studied utilizing CPT classification charts. Computation of the primary consolidation settlement due to preloading weight were carried out in PLAXIS 2D geotechnical software and verified against field measurements. A suggestion to protect the stabilized mass against severe weather condition was discussed.<br>Godkänd; 2013; 20130409 (makusa); Tillkännagivande licentiatseminarium 2013-04-25 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Gregory Paul Makusa Ämne: Geoteknik/Soil Mechanics and Foundation Engineering Uppsats: Mechanical Properties of Stabilized Dredged Sediments for Sustainable Geotechnical Structures Examinator: Professor Sven Knutsson, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Civ.ing. Forskningsdirektör Göran Holm, Statens Geotekniska Institut, Linköping Tid: Torsdag den 16 maj 2013 kl 10.00 Plats: F1031, Luleå tekniska universitet
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Cadwallender, Mary Virginia. "Comparative Landscape Infrastructure in Kolda, Senegal and Washington, D.C." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78321.
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This comparative study of two urban areas—Kolda, Senegal and the Historic Anacostia Neighborhood in Washington, D.C.—explores how landscape infrastructure can decrease the scalar disconnect between the global water crisis and local water use practices. By looking at one city in the Global North and one in the Global South with similar risk of water stress, I am able to compare cultural aesthetics and engage two different levels of infrastructural build out (World Resources Institute, Water Risk Atlas). The design approach draws inspiration from Lawrence Halprin's notion of "experiential equivalents," and proposes a suite of site scale water sources and seeps (Halprin, Ghirardelli Plaza). Unlike Halprin, whose designs primarily use, interpret, and express natural elements, cultural interactions with water as well as natural systems drive the designs in Kolda and Anacostia.
Thus, the speculative designs I am presenting weave the experiences of sourcing water, filtering water, and water seeps into the existing urban and cultural fabric. By taking a systemic and episodic approach to public landscape development, not only will these infrastructural landscapes serve the community but the aesthetic experience of the designs also becomes part of daily life. Perhaps as Elizabeth Meyer theorizes in "Beyond 'Sustaining Beauty'", these designed landscapes "can contribute to…]a new ethos of a sustainable perception and living." Furthermore, this project presents a kit of parts for community-based development, suggesting the ability to extend the landscape infrastructure systems in Kolda and Anacostia and providing the tools for other communities.<br>Master of Landscape Architecture
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Facun, Jasmine B. "Effects of Mowing Regimes on the Plants, Pollinators, and Roughness of the Channelized Hocking River’s Riparian Zone, Athens, Ohio." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1597248243432497.
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Bouyer, Laure. "Impact de la disponibilité en nutriments sur le fonctionnement hydrique et carboné de peupliers dans des contextes de sécheresse variés." Thesis, Orléans, 2019. http://www.theses.fr/2019ORLE3100.
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La disponibilité en eau et en nutriments sont deux facteurs limitant la croissance et la productivité des forêts. Malgré un historique important de travaux sur le rôle physiologique des principaux éléments minéraux, l’impact du statut nutritif des arbres sur leur capacité de réponse à la sécheresse demeure très largement inconnu. Cette thèse visait à évaluer le rôle de la disponibilité en nutriments sur des caractères clés indicateurs du fonctionnement hydrique et carboné comme la croissance et ses déterminants architecturaux, l’efficience d’utilisation de l’eau (WUE), la vulnérabilité à la cavitation ou encore les teneurs en glucides non structuraux, en réponse à des sécheresses d’intensités variées chez le peuplier. Deux dispositifs expérimentaux complémentaires ont été support des expériences, l’un en serre et l’autre en pépinière, et les travaux se sont concentrés sur un maximum de quatre génotypes sélectionnés pour leur comportement contrasté en termes de croissance et de régulation stomatique. Les résultats majeurs sont les suivants : 1) une disponibilité en nutriments plus importante augmente la croissance et WUE en conditions hydriques limitantes, 2) une disponibilité en nutriments plus importante n’augmente pas nécessairement les risques de dysfonctionnements hydrauliques, 3) l’épuisement des réserves carbonées, notamment de l’amidon, coïncide avec l’embolie massive du xylème à mortalité en cas de sécheresse sévère, et 4) une plus grande disponibilité en azote diminue la mise en réserve glucidique, notamment en condition de sécheresse modérée. Cette étude illustre pour la première fois de façon explicite la covariance au cours du temps entre les dysfonctionnements hydrauliques et l’épuisement des réserves chez une essence à croissance rapide très vulnérable à la sécheresse, et donne un exemple de la façon dont ces relations sont modulées par la disponibilité en nutriments<br>The availability of water and nutrients are two main factors limiting tree growth and forest productivity. Despite the strong legacy of research on forest nutrition, the role of nutrients in modulating tree drought responses remains largely unknown. This thesis aimed to evaluate the role of nutrient availability on key traits related to water and carbon relations such as growth and its determinants, water-use efficiency (WUE), vulnerability to cavitation, or non-structural carbohydrate (NSC) contents, in poplars under contrasting drought intensities. Research experiments relied on two complementary experimental designs, one in a greenhouse and the other in an outdoor common garden, and considered a maximum of four genotypes primarily selected for their contrasting growth and stomatal regulation. The main findings are as follows: 1) a higher nutrient availability increases growth and WUE under moderate drought, 2) a higher nutrient availability does not necessarily increase the risk of xylem hydraulic failure, 3) NSC depletion, in particular starch, co-occurs with massive xylem embolism under lethal drought, and 4) a higher nutrient availability reduces NSC storage, especially under moderate drought. This study shows for the first time the temporal covariance between the dynamics of xylem hydraulic failure and carbon starvation in a fast-growing but highly vulnerable tree species, and gives an example of how these relationships are modulated by nutrient availability
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Rizzo, Audrey. "L'approche CRONE dans le domaine des architectures complexes des suspensions de véhicules automobiles : la suspension CRONE Hydractive." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14564/document.
Full textAbstract:
Cette thèse s'inscrit dans la continuité des travaux de l'équipe CRONE appliqués à la suspension. Cette thèse permet de proposer une suspension CRONE qui non seulement gère le compromis Isolation vibratoire/ tenue de caisse mais également isolation vibratoire/ tenue de roue. Pour cela un critère est développé sur la tenue de roue, applicable à tous types de suspensions permettant l’analyse et le dimensionnement de la suspension pour le contrôle de roue. De plus afin de lever le dilemme entre sollicitations route et sollicitation conducteur, une stratégie pour les suspensions bi -états est proposée et appliquée sur suspension hydractive. Enfin , un travail de formalisme de l’ influence la suspension sur la dynamique véhicule fut réalisé permettant d ’enrichir la stratégie de commutation déjà développée pour agir en virage et en freinage et ainsi optimiser l’utilisation de la suspension<br>This thesis follows some previous work of the CRONE team applied to carsuspensions. It allows to purpose one car suspension, called CRONE car suspension, whichimproves the compromise between low frequency road filtering and car holding and thecompromise between hight frequency road filtering and wheel holding. To hold the wheel acriterium on the wheel holding is developed. This criterium can be used to analyse and tunedall kind of car suspension around the wheel pulsation. Moreover, to fight against thecompromise between the driver input and the raod input, a control laws is developed andapplied to a bi-state car suspension called hydractive car suspension. Finally, the influence ofthe car suspension tuning on the vehicle dynamic and more precisely on the ESP, ABSsystems is studied and illustrated with some first experiments
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Singley, Bradford G. "Computer-Based Instruction for Engineering Education in the Developing World." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2090.pdf.
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Saulich, Sven. "Generic design and investigation of solar cooling systems." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13627.
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This thesis presents work on a holistic approach for improving the overall design of solar cooling systems driven by solar thermal collectors. Newly developed methods for thermodynamic optimization of hydraulics and control were used to redesign an existing pilot plant. Measurements taken from the newly developed system show an 81% increase of the Solar Cooling Efficiency (SCEth) factor compared to the original pilot system. In addition to the improvements in system design, new efficiency factors for benchmarking solar cooling systems are presented. The Solar Supply Efficiency (SSEth) factor provides a means of quantifying the quality of solar thermal charging systems relative to the usable heat to drive the sorption process. The product of the SSEth with the already established COPth of the chiller, leads to the SCEth factor which, for the first time, provides a clear and concise benchmarking method for the overall design of solar cooling systems. Furthermore, the definition of a coefficient of performance, including irreversibilities from energy conversion (COPcon), enables a direct comparison of compression and sorption chiller technology. This new performance metric is applicable to all low-temperature heat-supply machines for direct comparison of different types or technologies. The achieved findings of this work led to an optimized generic design for solar cooling systems, which was successfully transferred to the market.
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Kocacinar, Ferit. "Photosynthetic pathway and hydraulic architecture in higher plants." 2004. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=80215&T=F.
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"Towards a hydraulic society: An architecture of resource perception." Thesis, 2010. http://hdl.handle.net/1911/62091.
Full textAbstract:
The earth has a finite supply of fresh water operating within a specific natural cycle. Due to population increases, massive industrialization of developing nations, and a culture of water consumption based on endlessness, the world is facing a massive crisis of freshwater shortage. Past and present solutions to local crisis have focused on supply management, when the real solution is demand management. Demand is founded on societal habits, cultural practices, and an individually based perception of water's value. The built environment mirrors this perception, where architecture as a cultural construct becomes an access terminal for various resource infrastructures. This thesis proposes an architecture that renders visible the cyclic specificity and finitude of water by proposing a new typology of public building that experientially transforms the inherited habits of citizens towards a balanced perception of water.
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Stevenson, Joshua Freedom 1970. "The safety of water movement and hydraulic architecture in cacti." 2002. http://hdl.handle.net/2152/11303.
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Stevenson, Joshua Freedom Mauseth James D. "The safety of water movement and hydraulic architecture in cacti." 2002. http://wwwlib.umi.com/cr/utexas/fullcit?p3106601.
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Link, Roman Mathias. "The role of tree height and wood density for the water use, productivity and hydraulic architecture of tropical trees." Thesis, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-13EF-9.
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Chenlemuge, xxx. "Drought Adaptation of the Fine Root System and Hydraulic Architecture of Larix sibirica at its Southern Distribution Limit General introduction." Doctoral thesis, 2014. http://hdl.handle.net/11858/00-1735-0000-0023-9980-9.
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Khansaritoreh, Elmira. "Effects of Land Use, Habitat Fragmentation and Climate Warming on Stem Increment, Regeneration, and Hydraulic Architecture of Larix sibirica in the Mongolian Forest-Steppe." Doctoral thesis, 2017. http://hdl.handle.net/11858/00-1735-0000-002E-E3EA-E.
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Kotowska, Martyna Małgorzata. "Carbon pools and sequestration in vegetation, litter dynamics and hydraulic anatomic properties in rainforest transformation systems in Indonesia." Doctoral thesis, 2015. http://hdl.handle.net/11858/00-1735-0000-0028-863B-9.
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Moura, Catarina. "Carbon and Water Relations in Pinus Taeda: Bridging the Gap across Plant Physiology, Genomics, and Global Climate Change." Diss., 2008. http://hdl.handle.net/10161/690.
Full textAbstract:
<p>Plants respond to changes in their local environment and, at the same time, influence the environment at a global scale. The molecular and physiological mechanisms regulating this interaction are not completely understood and this limits our capacity to predict the response of vegetation to future environmental changes. This dissertation combined tools from genomics, physiology, and ecology to examine the response of plants to environmental change. Specifically, it focused on processes affecting carbon and water exchange in forest trees because (1) trees are long-lived species that might face repeated environmental challenges; (2) relatively little information exists about the genes and the molecular mechanisms regulating structural and physiological traits in adult, long-lived woody plants; and (3) forest trees exchange a significant amount of carbon and water with the atmosphere and are therefore major players in the global carbon and water cycles. </p><p>Water flux through forests depends both on environmental conditions (e.g., soil moisture) and on the hydraulic architecture of individual trees. Resistance to xylem cavitation is an important hydraulic trait that is often associated with drought tolerance but potentially at the cost of reduced carbon uptake. The second chapter of this dissertation evaluated the variation in resistance to xylem cavitation, hydraulic conductivity, wood anatomy traits, and leaf gas exchange across 14 co-occurring temperate tree species including both angiosperms and gymnosperms. The relationship between vulnerability to cavitation (ψ<sub>50</sub>) and hydraulic conductivity within specific organs (i.e. stems and roots) was not significant when considering the phylogenetic association between species. However, even after phylogenetic correction, photosynthetic carbon uptake (A) was positively correlated with both stem and root ψ<sub>50</sub>, and stomatal conductance (g<sub>s </sub>) was strongly correlated with root ψ<sub>50</sub> . These results suggest that there is a trade-off between vulnerability to cavitation and water transport capacity at the whole-plant level, and that this functional relationship reflects an adaptive response to the environment. </p><p>Forests are an important component of the global carbon cycle that can be directly impacted by a rise in atmospheric CO<sub>2</sub> concentration.. The third chapter of this dissertation investigated the effects of long-term exposure to elevated CO2 on the gene expression of mature, field-grown loblolly pine trees. Using cDNA microarrays, I compared the expression of 1784 pine transcripts in trees growing under ambient and those under elevated CO<sub>2</sub> at monthly intervals throughout a growing season. Overall, more genes were upregulated than downregulated by elevated CO<sub>2</sub>, although the total number of genes differentially expressed varied throughout the season. The pattern of increasing number of differentially expressed genes until the peak of the growing season (July and August) followed by a decrease in that number, matched the seasonal trend of tree growth and photosynthetic response to elevated CO<sub>2</sub> in this species. The seasonal trend also reflected the interaction among multiple abiotic factors intrinsic to field conditions and emphasized the relevance of evaluating the role of genes in their natural environment. Genes consistently upregulated by elevated CO<sub>2</sub> were functionally associated with environmental sensing, cellular signaling, and carbon metabolism, in particular the degradation of carbohydrates through respiration. An increase in carbohydrates degradation is particularly relevant in the context of carbon balance of forest trees because of the potential for enhanced leaf and tree respiration leading to a reduced sink capacity for CO<sub>2</sub>. </p><p>Loblolly pine produces several flushes of needles throughout the year each with an average lifespan of 19 months. Each year, two age classes of needles contribute to the annual carbon sequestration of the loblolly pine forest. To address the impact of leaf age on the effects of elevated CO<sub>2</sub> in carbon metabolism regulation, I compared the gene expression profiles from trees under ambient and elevated CO<sub>2</sub> conditions in two needle cohorts: one-year-old and current-year. Differential expression under elevated CO<sub>2</sub> was seven times more frequent in current-year than in one-year-old needles. Despite differences in magnitude, many of the patterns within specific groups of genes were similar across age classes. For instance, there was a trend for downregulation of genes involved in the light-reactions of photosynthesis and those in photorespiration in both age classes, while genes associated with dark respiration were largely upregulated by elevated CO<sub>2</sub> in both cases. The difference between the two cohorts was particularly evident in the group of genes related to energy production (ATP synthesis) and the group associated with carbon partitioning (sucrose and starch metabolism). Because sucrose and starch metabolism categories included many genes known to be important regulators of gene expression and plant physiological processes, this suggests that this stage of carbon metabolism might be an important control point in age-dependent foliar responses to elevated CO<sub>2</sub>.</p><p>This dissertation examined both structural and physiological components of plant water and carbon relations (Chapter 2) across different biological scales of organization (whole-plant level in Chapter 2; gene-level response to ecosystem-level changes in Chapters 3 and 4) and reflecting adjustments at distinct temporal scales (life-span of the organism vs. evolutionary selection of traits). An integrative approach was used to advance our understanding of how plants acclimate and adapt to their environment, and to provide a mechanistic framework for predictive models of plant response to environmental change. </p><br>Dissertation
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Schuldt, Bernhard. "Effects of experimental drought on hydraulic properties and leaf traits of upper canopy and understory tree species in a perhumid tropical forest in Central Sulawesi, Indonesia." Doctoral thesis, 2010. http://hdl.handle.net/11858/00-1735-0000-0006-ADD8-8.
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Gebauer, Tobias. "Water turnover in species-rich and species-poor deciduous forests: xylem sap flow and canopy transpiration." Doctoral thesis, 2009. http://hdl.handle.net/11858/00-1735-0000-0006-AD85-F.
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(9750938), Leandro Henschel Danes. "COMPUTATIONAL METHODS FOR DESIGNING NEW PASSIVE FLUID BORNE NOISE SOURCE REDUCTION STRATEGIES IN HYDRAULIC SYSTEMS." Thesis, 2020.
Find full textAbstract:
<p>Hydraulic
systems have many applications in the construction, transportation, and
manufacturing sectors. Recent design trends involve systems with higher working
pressures and more compact systems, which are advantageous because of power
density increase. However, these trends imply higher forces and larger
vibration amplitudes while having lesser mass and damping, leading to higher
noise levels. Meanwhile, hydraulic machinery started prospecting new
applications with tighter noise regulations, a trend which was also pushed by
the electrification tendency in several fields of transportation and
agriculture. One method to attain noise mitigation is passive-noise canceling
techniques have the advantage of not introducing energy to the system. This
approach arranges pressure ripple waves in a destructive pattern by projecting a
hydraulic circuit's geometry, configuration, and features.</p>
<p> </p>
<p>This
dissertation aims to predict fluid-borne noise sources and investigate passive
noise-canceling solutions for multiple operations conditions targeting to
impact many hydraulic systems and a broad range of operating conditions. Primarily
a coupled system model strategy that includes a one-dimensional line finite
element model is developed. The line model predicts pressure wave generation
and propagation. The model features versatility since parameters like line
diameter and material can be discretized node by node. Simulations are compared
to measured data in a realistic novel hydraulic hybrid transmission for validation.
</p>
<p> </p>
<p>Subsequently,
an extensive numerical investigation is performed by setting fixed
parameters along the hydraulic lines' length and comparing several isolated
geometric properties in simulation. The developed line model is also used to
study the influence of line features such as diameter and extent of the
conduit. Cost-effective and simple passive solution solutions such as Quincke
tubes (parallel lines), expansion chambers, and closed branches are selected
and investigated on simulation. Four target pressure ripples are chosen as indicators
for summarizing passive line elements behavior. The frequency-domain behavior
of the pressure ripple peaks regarding the line's length is identified and
isolated in simulation at the 50-5000Hz frequency spectrum. An experiment test rig is designed to
implement these solutions and the experiments show three developed passive
elements as practical and effective solutions for reducing fluid borne noise sources.
The selected designs yielded noise source attenuation over most of the frequency
spectrum measured with piezoelectric pressure variation sensors and
accelerometers in different positions in the hydraulic circuit. Sound pressure
measurements detected reductions over 3dB in the best cases. </p>
<p> </p>
<p>Also,
a passive interference approach based on the principle of secondary source flow
ripple cancellation was conceptualized, modeled, and implemented in a tandem
axial-piston unit. The strategy consists of setting the phase between the two
synchronous units to accomplish destructive interference in targeted unit
harmonics. Two indexing strategies are investigated first analytically and then
on simulation. One of the indexing strategies was implemented in a pre-existent
commercial axial-piston tandem unit.
Experiment results confirmed effectiveness for the first and third
unit’s harmonics, where reductions over 15dB on pressure ripple were measured.</p>
<p> </p>
<p>Finally,
a fluid-structure interaction based on the poison coupling principle is
developed using the method of characteristics. Transfer functions of the
pipeline accelerations versus the pressure ripples on lines calculated on
simulation and later obtained experimentally to highlight ta critical vibration
band from 2000Hz to 3000Hz with high acceleration response.</p>
<p> </p><br>
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Fernández, López-Leitón Ramón. "Significación del agua urbana: mejora del espacio público mediante la recuperación de la importancia del agua." Master's thesis, 2018. http://hdl.handle.net/10284/6670.
Full textAbstract:
El empobrecimiento del espacio urbano de nuestras ciudades es un hecho del cual cada
día hay mayor consciencia. En un contexto globalizado y de abrumadora artificialidad el
ciudadano pierde la conexión con la identidad histórica de su ciudad al mismo tiempo
que con el medio que le rodea.
Se pretende aquí hablar de estrategias que permitan revertir esta situación,
renaturalizando la ciudad, al mismo tiempo que fortaleciendo la relación con sus raíces
históricas y proponiendo soluciones pensadas para las condiciones enormemente
cambiantes del futuro.
La base de este trabajo es la de relacionar esta mejora del espacio público con la
recuperación de la importancia del agua urbana, de su significación. Se estudiarán estas
interacciones en diferentes momentos históricos de la humanidad así como en proyectos
de intervención urbana más concretos y recientes.
El objetivo no es más que la síntesis de determinados conceptos que puedan servir de
ayuda para la reflexión durante el proceso de diseño de un proyecto urbano futuro, en el
que el líquido elemento pueda jugar un notable papel.<br>The impoverishment of our city’s urban space is a fact with awareness that grows each
day. In a globalized and overwhelmingly artificial context, citizens lose their connection
with the true historical identity of their cities and the environment that surrounds them.
The intention here is to outline strategies that allow the reversal of this situation,
reevaluating the city while strengthening its connection with its historical roots and
introducing solutions designed for the enormously changing conditions of the future.
The basis of this work is to link the improvement of public spaces with the recovery of
the importance of urban water and its significance. These interactions will be studied in
different historical moments of humanity as well as more recent and focused urban
intervention projects.
The goal is no more than to synthesize specific concepts that can help design future
urban projects in which the liquid element plays a crucial role.