Abstract There are various after-use options on the cut-away peatlands, depending on the characteristics of the soil. If the soil is devoid of rock, cultivation of reed canary grass is a profitable after-use option. The aim of this study was to determine how characteristics of peat, peatland surroundings and fertilizers influence the element uptake of reed canary grass. In the present investigation the peat production areas of Luesuo, Piipsanneva and Jouttenisenneva were selected as study areas. A comprehensive sampling programme was carried out in each of the study areas. In addition, two experimental areas for cultivation of reed canary grass were established in Luesuo and Hankilanneva between 2004 and 2005. The results obtained indicate that all study areas were suitable for cultivating reed canary grass, but fertilizers must be added to make up nutrient deficiencies. The study areas were very clean from heavy metals. The results also suggest that the characteristics of peat or surroundings of peatland do not influence the nutrient level of peat significantly, considering the cultivation of reed canary grass. The large geochemical provinces have a smaller impact on nutrient and heavy metal levels in the peat on the peat cut-away areas compared to smaller geochemical units. Heavy metal content in the peat and in the mineral soil under the peat seems to correlate. Reed canary grass does not uptake heavy metals from the cultivation media effectively. Liming slag was better for liming in cultivation of reed canary grass than ash. Although ash has large amounts usable nutrients, especially potassium, it did not raise the heavy metal content in peat to harmful levels, it can therefore be used in the cultivation of reed canary grass. Stock fertilized fur animal manure compost produced almost as much biomass as optimized artificial fertilizers. After the correction of nutrient deficiencies, compost is suitable for the cultivation of reed canary grass in peatlands. Because the total nutrient levels are high in compost, its fertilizer effect lasts longer than in artificial fertilizers, where nutrients are all in a dissolved form. Already in the first growing season the cultivation of reed canary grass changed the cut-away peatland from a carbon source to a carbon sink. In this respect, the reed canary grass cultivation can be used to produce bioenergy to replace fossil fuels in accordance with the goals of Kyoto Protocol. / Tiivistelmä Turvetuotannosta vapautuneella suopohjalla toteutetaan erilaisia jälkikäyttötapoja riippuen suopohjan ominaisuuksista. Jos suopohja on kohtuullisen kivetöntä, ruokohelpiviljely on kannattavaa. Viljelty ruokohelpi poltetaan turpeen tai hakkeen seassa. Tämän tutkimuksen tarkoitus oli selvittää miten pohjaturpeen ja suopohjan ympäristöalueiden ominaisuudet sekä viljelyyn käytetyt lannoite- ja kalkitusaineet vaikuttavat ruokohelpin käyttämiin ravinteisiin. Ruokohelpiviljelyn lannoituskustannukset ovat suuret, joten suopohjan luontainen ravinnetila kannattaa huomioida lannoitusta suunniteltaessa. Suopohjan ravinnetila saadaan selville laatimalla alueelle viljavuusanalyysi. Kyseisen analyysin yhteydessä on hyödyllistä tehdä myös raskasmetallianalyysit, jotta viljelykäyttöön tulevan suopohjan puhtaudesta voidaan varmistua. Tutkimuksen kohdealueiksi valittiin Luesuon, Piipsannevan ja Jouttenisennevan turvetuotantoalueet. Lisäksi tutkimusta varten perustettiin ruokohelpin viljelykoealueet Luesuolle ja Hankilannevalle vuosina 2004 ja 2005. Tutkimusalueilla suoritettiin kattava näytteenotto. Näytteistä analysoitiin tärkeimmät kasviravinteet sekä joukko raskasmetalleja. Tulosten perusteella tutkimusalueille laadittiin viljavuusluokittelu. Tutkimusalueet soveltuvat hyvin ruokohelpiviljelyyn, mutta ravinnepuutokset tulee korjata lannoituksella käytettäen suopohjille suositeltua lannoitusta. Tutkimusalueet osoittautuivat puhtaiksi raskasmetalleista. Tutkimuksen kohteina olleiden suopohjien liukoisen kaliumin ja fosforin pitoisuudet olivat hyvin alhaisia, eivätkä turpeen tai ympäristön ominaisuudet vaikuttaneet niiden pitoisuuksiin ruokohelpiviljelyn kannalta merkittävästi. Liukoisen magnesiumin ja kalsiumin pitoisuudet sen sijaan vaihtelivat tutkituilla suopohjilla kohtuullisen paljon riippuen turpeen ominaisuuksista. Geokemiallisella provinssilla ei todettu olevan niin suurta merkitystä suopohjien lopputurpeiden alkuainepitoisuuksiin kuin pienemmillä geokemiallisilla yksiköillä. Tutkittujen suopohjien turpeen ja sen alla olevan kivennäismaan raskasmetallipitoisuudet korreloivat keskenään. Tutkimustulosten mukaan kasvualustan raskasmetallit eivät siirry tehokkaasti ruokohelpiin. Poikkeuksena olivat sinkin ja molybdeenin pitoisuudet, joita ruokohelpissä esiintyi korkeampina pitoisuuksina kuin kasvualustassa. Haitallisten raskasmetallien pitoisuudet olivat huomattavasti alhaisempia ruokohelpissä kuin kasvualustassa. Ruokohelpi sisälsi raskasmetalleja erittäin pieninä pitoisuuksina, joten viimeisen kasvukuukauden muutokset olivat vaikeasti tulkittavissa. Näyttää kuitenkin siltä, että ruokohelpi siirtää ainakin osan kuparista, sinkistä ja molybdeenistä juuristoonsa talven ajaksi. Suoritettujen lannoituskokeiden perusteella teräskuona soveltuu voimalaitostuhkaa paremmin turvekentän kalkitukseen ruokohelpiviljelyssä. Voimalaitostuhka sisältää kuitenkin huomattavia määriä hyödynnettäviä ravinteita, etenkin kaliumia. Tutkimuksessa havaittiin, ettei voimalaitostuhka lisännyt edes ylisuurina annoksina kasvualustan raskasmetallipitoisuuksia haitallisesti, joten sitä voidaan käyttää ruokohelpiviljelyssä. Varastolannoitetulla kompostilla saavutettiin lähes yhtä hyvä ruokohelpisato kuin optimoidulla mineraalilannoitteella. Näin ollen turkislantakompostia voidaan ravinnekorjausten jälkeen käyttää mainiosti ruokohelpiviljelyyn. Kompostin ravinnevaikutus on myös suurten kokonaisravinnepitoisuuksien vuoksi pidempi kuin mineraalilannoitteilla. Fosforin varastolannoitus turkislantakompostilla onnistui ensimmäisen kasvukauden perusteella hyvin. Tutkimuksessa todettiin, että jo ensimmäisenä kasvukautena ruokohelpiviljelyllä saadaan muutettua hiililähteenä toimiva entinen turvetuotantoalue hiilinieluksi. Ruokohelpiviljelyllä tuotetulla bioenergialla voidaan lisäksi korvata fossiilisia polttoaineita Kioton ympäristösopimuksen tavoitteiden mukaisesti.

Pour répondre à la demande mondiale croissante en huile et en protéines, le tournesol apparaît comme une culture très compétitive grâce à la diversification de ses débouchés et son attractivité environnementale et nutritionnelle. Pourtant, les teneurs en huile et protéines sont soumises à des effets génotypiques et environnementaux qui les rendent fluctuantes et difficilement prédictibles. Nous argumentons qu’une meilleure connaissance des effets les plus importants et leurs interactions devrait permettre de mieux prédire ces teneurs. Deux approches de modélisation ont été développées. Dans la première, trois modèles statistiques ont été construits puis comparés à un modèle simple existant. L’approche dynamique est basée sur l’analyse des relations source-puits au champ et en serre (2011 et 2012) pendant le remplissage. Les performances et domaines de validité des deux types de modélisation sont comparés. / Considering the growing global demand for oil and protein, sunflower appears as a highly competitive crop, thanks to the diversification of its markets and environmental attractiveness and health. Yet the protein and oil contents are submitted to genotypic and environmental effects that make them fluctuating and hardly predictable. We argue that a better knowledge of most important effects and their interactions should permit to improve prediction. Two modeling approaches are proposed: statistical one, where we compared three types of statistical models with a simple existing one. The dynamic approach is based on source-sink relationships analysis (field and greenhouse experiments in 2011 and 2012) during grain filling. Performances of both modeling types and their validity domain are compared.

Cette thèse porte sur le développement d'un ensemble d'outils numériques destinés à simuler différents aspects des interactions vagues-structure appliquées à l'exploitation des systèmes de récupération de l'énergie des vagues (SREV). Elle a été réalisée dans le cadre du projet ANR Monacorev (projet ANR11-MONU-018-01, 2012-2015).L'objectif est de pouvoir traiter la question des interactions à l'échelle d'une ferme de SREVs (≈ 1 km), et d'étudier l'impact d'une ou plusieurs fermes de SREVs à l'échelle régionale (≈ 10km) sur le champ de vague total. Des méthodes de modélisation et de simulation adaptées sont développées pour chacune de ces deux échelles. Jusqu'à présent, les interactions entre les SREVs étaient bien souvent étudiées en considérant que le fond était plat (l'influence d'un fond variable sur le champ de houle au niveau de la ferme étant alors jugé négligeable), ce qui permet de calculer facilement et rapidement le champ de vagues et les interactions grâce à l'utilisation de la théorie linéaire potentielle. Une application pratique de cette méthode est le calcul du rendement d'une ferme de SREVs, et l'optimisation de leurs positions relatives au sein d'un parc. Dans le cadre de la théorie linéaire, cette thèse propose une méthodologie de couplage originale entre un code de tenue à la mer (Aquaplus) et un code de propagation de la houle en zone côtière (Artemis), laquelle a été développée et qualifiée. Les simulations réalisées montrent que, pour une configuration de ferme de SREVs donnée, on ne peut pas toujours négliger les effets de la bathymétrie. Par exemple, la présence d'une plage de pente 10% au large d'une ferme de SREV peut modifier la hauteur des vagues de manière significative, et affecter ainsi le rendement de la ferme de manière significative par rapport au cas où le fond est uniformément plat. A l'échelle côtière régionale, il est aussi intéressant de simuler et prédire l'impact de fermes de SREVs sur le champ de vagues. Pour des raisons d'efficacité, une approche à phases moyennées de modélisation des vagues a été privilégiée, fondée sur le code spectral d'états de mer Tomawac. La représentation des effets d'un SREV à travers l'utilisation d'un terme puits (concept permettant de soustraire au spectre d'énergie d'état de mer local l'énergie correspondant à celle absorbée par le SREV), bien qu'incomplète du fait que les effets de radiation/diffraction ne sont pas pris en compte, a été étudiée et testée. Une nouvelle méthodologie prenant en compte ces effets dans un code spectral est présentée ici et testée, avec l'objectif de pallier à ces limitations. Les discussions sur la validité de deux approches permettent d'esquisser des pistes de développements ultérieurs pour la représentation des fermes de SREV à l'échelle régionale / This thesis focuses on the development of a set of numerical tools to simulate different aspects of the wave-body interactions applied to the exploitation of wave energy converters (WEC). It was conducted under the ANR Monacorev project (project-ANR11 MONU-018-01, 2012-2015).The objective is to address the issue of the interactions at the scale of a farm of WECs (≈ 1 km), and to study the impact of one or more WEC farms at the regional scale (≈ 10km ) on the total wave field. Modeling and simulation methods adapted for each of these two scales are developed. Until now, the interactions between WECs was often studied by considering that the bottom was flat (the influence of a variable bathymetry on the wave field at the farm site being considered to be negligible), allowing to easily and quickly calculate the wave field and interactions through the use of linear potential theory. A practical application of this method is the yield estimation for a WEC farm and the optimization of the WEC position within a park. In the framework of the linear theory, this thesis proposes an original coupling methodology between a seakeeping (Aquaplus) and a wave propagation code in coastal areas (Artemis), which was developed and qualified. Simulations show that, for a given WEC farm configuration, effects of the bathymetry cannot systematically ignored. For example, the presence of a 10% slope close to a WEC farm can significantly modify the wave height, and thus affect the performance of the farm by several percent compared to the case with a uniformly flat bottom. At the regional coastal scale, it is also interesting to simulate and predict the impact of WEC farms on the wave field. At this scale, for efficiency reasons, a phase-averaged simulation of waves was preferred, based on the sea state spectral code TOMAWAC. The representation of the effects of a WEC through the use of a sink-term (concept for subtracting the energy equivalent to that absorbed by the WEC to the sea state energy spectrum), though incomplete due to the fact that the scattering effects are not taken into account, has been studied and tested. A new methodology taking into account these effects in a spectral code is presented here and tested with the aim to overcome these limitations. Discussions on the validity of these approaches allow us to propose possible future developments for the modeling of WEC farm at the regional scale

Sensor nodes in a wireless sensor network (WSN) have a small, non-rechargeable power supply. Each message transmission or reception depletes a sensor node’s energy. Many WSN applications are ad-hoc deployments where a sensor node is only aware of its immediate neighbours. The lack of a predefined route path and the need to restrict the amount of communication that occurs within the application area impose constraints on WSNs not prevalent in other types of networks. An area of active research has been how to notify the central sink (or monitoring hub) about an event in real-time by utilising the minimum number of messages to route a message from a source node to the destination sink node. In this thesis, strategies to limit communication within a WSN application area, while ensuring that events are reported on and responded to in real-time, is presented. A solution based on modelling a WSN as a small world network and then transmitting an initialisation message (IM) on network start-up to create multiple route paths from any sensor node to one or more sinks is proposed. The reason for modelling a WSN as a small world network is to reduce the number of nodes required to re-transmit a message from a source sensor node to a sink. The purpose of sending an IM at network start-up is to ensure that communication within the WSN is minimised. When routing a message to a static sink, the nodes closest to the static sink receive a disproportionate number of messages, resulting in their energy being consumed earlier. The use of mobile sinks has been proposed but to our knowledge no studies have been undertaken on the paths these mobile sinks should follow. An algorithm to determine the optimum path for mobile sinks to follow in a WSN application area is described. The purpose of an optimum path is to allow more equitable usage of all nodes to transfer an event message to a mobile sink. The idea of using multiple static sinks placed at specific points in the small world model is broadened to include using multiple mobile sinks called actors to move within a WSN application area and respond to an event in real-time. Current coordination solutions to determine which actor(s) must respond to the event result in excessive message communication and limit the real-time response to an event. An info gap decision theory (IGDT) model to coordinate which actor or set of actors should respond to the event is described. A comparison of the small world routing (SWR) model against routing using flooding and gossiping shows that the SWR model significantly reduces the number of messages transmitted within the network. An analysis of the number of IMs transmitted and received at individual node level shows that prudent selection of the hop count (number of additional nodes required to route a message to sink) to a sink node will result in a reduced number of messages transmitted and received per node within the network. The use of the IGDT model results in a robust decision on the actor(s) chosen to respond to an event even when uncertainty about the location and available energy of other actor(s) exists. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted

La performance d'une plante repose en partie sur sa capacité à capturer l'énergie lumineuse via la croissance foliaire. La littérature souligne deux limitations majeures de la croissance, de nature métabolique ou hydraulique. Nous testons ici l'hypothèse originale que l'importance relative de ces deux limitations est structurée par l'ontogenèse de la feuille chez Arabidopsis thaliana. Nous montrons que la disponibilité en carbone restreint la croissance des jeunes feuilles, tandis qu'une compétition hydraulique entre croissance et transpiration s'accroît au cours de l'ontogenèse. La mise en place de cette limitation hydraulique s'explique par une dégradation de la capacité du xylème et probablement des aquaporines à approvisionner la feuille en eau, malgré une diminution ontogénétique de la transpiration. Cette dernière est la conséquence de l'acquisition progressive de la sensibilité des stomates aux signaux de fermeture, notamment l'obscurité et l'acide abscissique (ABA), hormone induite par la sécheresse. Enfin, nous mettons en évidence une nouvelle composante de la sensibilité stomatique à l'ABA, conservée chez des mutants décrits comme insensibles à cette hormone : l'ABA induit une diminution de la conductance hydraulique foliaire qui abaisse le potentiel hydrique foliaire et in fine la conductance stomatique. Ce mécanisme chez les feuilles développées contribuerait sous stress hydrique à rediriger le flux d'eau vers les feuilles en croissance. Plus généralement, le contrôle des stomates par des mécanismes hydrauliques induits par l'ABA pourrait être une composante majeure de l'ajustement entre offre et demande en eau chez les plantes soumises à un stress hydrique. / In plants, leaf growth is the central process allowing energy capture and space colonization. The literature suggests that leaf growth is predominantly determined by metabolic and hydraulic limitations. Here, we test the original hypothesis that the relative importance of metabolics and hydraulics on the control of leaf growth is organized according to leaf ontogeny in Arabidopsis thaliana. We show that leaf carbon balance limits growth of the young leaves which therefore grow at a slower rate in the nighttime, while a hydraulic limitation gradually establishes in the daytime, when growth and transpiration competes for water. This gradual hydraulic limitation is underlain by a deterioration of leaf venation and probably aquaporins capacity to supply water to the leaf, despite an ontogenetic decrease in transpiration. This decline in transpiration occurs because stomata acquire throughout leaf ontogeny their sensitivity to the major closure signals, including darkness and abscisic acid (ABA), a hormone induced by drought. Finally, we discover a novel component of stomatal sensitivity to ABA, conserved in mutants described as insensitive to ABA in isolated epidermis: ABA induces a decrease in leaf hydraulic conductance which lowers leaf water potential and stomatal conductance according to a hydraulic cascade. Decreasing leaf hydraulic conductance through ABA action in fully expanded leaves would contribute to redirect water flow to the young leaves under water stress. More generally, controlling stomata by ABA-induced hydraulic mechanisms could be a crucial component of the coordination between water supply and water demand in plants under water challenging conditions.

El presente trabajo de investigación trata de la influencia de la inclinación de pozas disipadoras en la pérdida de energía en ríos de alta pendiente. Para ello, se tomó como caso de estudio la bocatoma San Pedro (Ayacucho, Perú). Se presenta el modelamiento numérico de la bocatoma en el software de dinámica de fluidos computacional, IBER, con el fin de obtener resultados hidráulicos en la estructura: tirante, velocidad, energía, Froude y tensión de fondo. El principal objetivo es mejorar la eficiencia del funcionamiento de las pozas disipadoras en ríos de alta pendiente. Asimismo, conocer las características hidráulicas del río San Pedro, que representa un flujo de alta pendiente. La metodología empleada fue la recoilación de información del caso de estudio, la cual fue validada con los resultados de los modelamientos en los programas HEC-RAS e IBER. Del mismo modo, se diseñaron 5 bocatomas con pozas disipadoras de distintas pendientes: 0%, 1.52%, 3.04%, 4.56% y 6.08%. Se modelaron en el software IBER y se exportaron los resultados a Excel. Estos modelos numéricos fueron validados mediante el Análisis de Sensibilidad. En consecuencia, se compararon los valores de energía aguas abajo de las distintas pozas propuestas. Finalmente, con los resultados del estudio se concluye que la poza disipadora de 3.04% es la más apropiada para el río San Pedro, pues pierde un 30% de energía más con respecto a la poza horizontal y reduce la velocidad en 4.9% en comparación a la poza de inclinación de 6.08%. / This research work deals with the influence stilling basin slope on energy loss in high slope rivers. Taking as a case study the water intake San Pedro (Ayacucho, Peru). Numerical modeling of water intake is presented in computational fluid dynamics software, IBER, in order to obtain the hydraulic results in the structure: hydraulic depth, velocity, energy, Froude and shear stress. The main objective is to improve efficiency of stilling basins operation in rivers with high slope. Also, know the hydraulic characteristics of the San Pedro River, which represents a high slope river. The methodology used was the collection of case study information, was validated with the results of modeling in the HEC-RAS and IBER programs. Similarly, five dissipation basins of different slopes were modeled: 0%, 1.52%, 3.04%, 4.56% and 6.08%. They were modeled in IBER software, and the results were exported to Excel. These numerical models were validated by Sensitivity Analysis. Consequently, the downstream energy values of the different proposed stilling basins were compared. Finally, the results of the study conclude that the 3.04% slope dissipative basin is the most appropriate for the San Pedro river, as it loses 30% more energy than the horizontal basin and reduces the velocity by 4.9% compared to the 6.08% inclined basin. This proposed stilling basins will feature an alphaizer on the End of the breakwater that will be calculated with Peterka's monograph shown in the bibliography. / Tesis

This thesis deals with the problem of waste heat, namely, the exhaust gas which are not frequently used. Specifically, it is a design of thermoelectric generators set, power electronics for fan and heat exchanger proposal. The entire system uses the energy of the waste heat to increase the heating efficiency.

In this thesis an alternative exterior wall construction for a specific building isinvestigated. The focus has been on investigating the material straw as a possiblecomponent in the future project Kulturborgen in Skåne, Sweden.Straw is a bio-based building material which, with a consideration to the climate crisis,has become a viable alternative intended to minimize carbon dioxide emissions from thebuilding sector. Through a compilation of the latest research on the material, theproperties of straw are presented in the theory chapter. Previous studies have shown thepotential of straw to be used as a load-bearing frame in house construction. However, dueto an adaptation to existing blueprints, the focus in this project has been on using straw asonly an insulating material together with load bearing I-joists. By modeling in AutodeskRevit and making calculations on the structure's load bearing capacity and thermalinsulation, a solution on an outer wall has been presented. The work culminates in aproposal for detailed drafts for a specific building that can become the basis for a possiblefurther development. / Halm är en restprodukt från odling av säd och andra grödor och räknas ur miljösynpunkttill ett mer hållbart alternativ än de konventionella byggnadsmaterial som producerasidag. Växtbaserade byggnadsmaterial som halm kan utgöra kolsänkor tack vare sinförmåga att fånga upp koldioxid från atmosfären och med tanke på en störreklimatmedvetenhet har biobaserade material blivit ett aktuellt alternativ ämnat attminimera koldioxidutsläppet från byggbranschen. Tidigare studier visar att halm har godaförutsättningar att användas som ett isolerande material tack vare sin lågavärmekonduktivitet. Halm kan även användas som en självbärande stomme eftersom denhar en hög lastöverföringsgrad. I kombination med en regelkonstruktion av annat materialkan halmen användas enbart som ett isolerande skikt mellan reglarna.Kulturborgen är ett storskaligt byggnadskomplex projekterat som en ringborg med ettöppet torg i mitten. Den byggnad som har studerats i detta examensarbete är enbart en deli komplexet, nämligen ett vandrarhem i två plan. I arbetet undersöks de möjligheter somfinns när en betongväggkonstruktion ersätts med ett biobaserat alternativ samt vilkakonsekvenser det kan få för projekteringen.I detta examensarbete undersöks en alternativ ytterväggskonstruktion för Kulturborgen.Fokus har varit att undersöka materialet halm som en möjlig beståndsdel i det framtidaprojektet Kulturborgen i Skåne, där den ursprungliga planen var att uppföra byggnadenmed prefabricerade betongelement.I en sammanställning av den senaste forskningen om materialet har halmens egenskaperoch tillämpning inom byggbranschen redovisats i ett teorikapitel. Olika metoder för attanvända halm som ett byggnadsmaterial har också tagits upp med avsikt att undersökavilken byggnadsmetod som passar bäst för Kulturborgen.På grund av anpassning till befintliga ritningar på Kulturborgen har användningen avhalm i detta projekt behandlats som enbart ett isoleringsmaterial där halmen är ett 400mm isolerande skikt i kombination med lättreglar med en bärande funktion. Lättreglarvaldes därför att de tack vare sitt I-tvärsnitt har en lägre andel trä än en regel med ettrektangulärt tvärsnitt. Detta gör att lättreglar är materialbesparande och ett lägre U-värdekan erhållas.En modell har tagits fram genom användning av programmet Autodesk Revit.Beräkningar på lättreglar har gjorts för att säkerställa att byggnaden klarar av alla lasterden utsätts för. U-värdesberäkningar utfördes för att kontrollera att vägguppbyggnadensom valdes fick ett U-värde som låg under 0,15 W/m2K, vilket hamnar inom en rimliggräns för en yttervägg. Slutligen har en lösning på en ytterväggskonstruktion presenterats.Arbetet mynnar ut i ett förslag på detaljlösningar för Kulturborgens vandrarhem ochdessa kan ligga till grund för en eventuell vidareutveckling.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18582号 / 工博第3943号 / 新制||工||1606(附属図書館) / 31482 / 京都大学大学院工学研究科建築学専攻 / (主査)教授 加藤 直樹, 教授 門内 輝行, 教授 神吉 紀世子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The size of the IoT network is expanding due to advancements in the IoT field, leading to increased interest in the multi-sink mechanism. The IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) is a representative IoT protocol that focuses on the Low-Power and Lossy Networks. However, research on comparing multi-sink strategies within the RPL network is limited. Therefore, this project aims to compare three common strategies: multiple-DODAG in one instance, virtual root, and multiple-instance. Using these strategies, we design and implement RPL networks and conduct simulations in various scenarios. Five different topologies are utilized in the experiments, considering different packet loss rates. Performance evaluation of each strategy is conducted using the Cooja simulator and Contiki-NG system, with a focus on the number of RPL control packets, Packet Delivery Ratio (PDR), and energy consumption. The results indicate that both the virtual root and multiple-DODAG strategies perform well with low packet loss, while the virtual root strategy outperforms the multiple-DODAG strategy with high packet loss. Additionally, the virtual root strategy incurs slightly higher energy costs than the multiple-DODAG strategy. Furthermore, the multiple-instance strategy demonstrates poor performance in most scenarios, except for the packet delivery ratio under high packet loss conditions. Besides the analysis, potential areas for future research on the RPL’s multi-sink mechanism are finally identified. / Storleken på IoT-nätverket expanderar på grund av framsteg inom IoT-området, vilket leder till ökat intresse för multi-sink-mekanismen. IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) är ett representativt IoT-protokoll som fokuserar på Nät med låg effekt och förluster. Forskningen om jämförelse av multi-sink-strategier inom RPL-nätverket är dock begränsad. Därför syftar detta projekt till att jämföra tre vanliga strategier: multiple - DODAG i en instans, virtuell rot och multi-instans. Med hjälp av dessa strategier designar och implementerar vi RPL-nätverk och genomför simuleringar i olika scenarier. Fem olika topologier används i experimenten, med olika packet loss rate. Prestationsutvärdering av varje strategi utförs med hjälp av Cooja-simulatorn och Contiki-NG-systemet, med fokus på antalet RPL control packets, Packet Delivery Ratio (PDR) och energiförbrukning. Resultaten indikerar att både virtuell rot och multiple-DODAG strategier fungerar bra vid låg datapaketförlust, medan den virtuella rotstrategin överträffar multiple-DODAG strategin vid hög datapaketförlust. Dessutom medför den virtuella rotstrategin något högre energikostnader än flera DODAG-strategin. Dessutom visar multi-instans-strategin dålig prestanda i de flesta scenarier, förutom när det gäller datapaketleveransförhållandet under höga datapaketförlustförhållanden. Utöver analysen identifieras slutligen potentiella områden för framtida forskning om RPL-protokollets multi-sink-mekanism.