Reconfigurable remote nodes for hybrid passive optical networks

Mestrado em Engenharia Electrónica e TelecomunicaçõesO presente documento tem por objectivo demonstrar, analisar e optimizar nós remotos passivos para redes ópticas passivas baseadas numa topologia de anel de dupla fibra com multiplexagem no comprimento de onda onde estão penduradas árvores mono fibra baseadas na multiplexagem no tempo. A rede ‘Scalable Advanced Ring-based passive Dense Access Network Architecture’ (SARDANA) baseada nesta topologia é apresentada e demonstrada. Na rede SARDANA a interligação entre o anel e as árvores é realizada pelo intermédio de um nó especial denominado de nó remoto. Esse nó remoto é um elemento fundamental para o funcionamento, resiliência e escalabilidade da rede. Neste documento são apresentadas e comparadas diferentes topologias para a implementação desse nó remoto. É também apresentada a reconfigurabilidade remota desses mesmos nós remotos através de módulos de conversão energética e controlo, implementada nos nós remotos. Um factor importante para a optimização dos nós remotos é a amplificação remota realizada por intermédio de fibras dopadas de érbio pelo que o seu estudo é também apresentado. Finalmente é demonstrado um protótipo de um nó remotamente reconfigurado e eficiente. ABSTRACT: The objective of this document is to demonstrate, analyze and optimize remote nodes for passive optical networks based on double fiber ring multiplexed in wavelength connected to single fiber trees multiplexed in time. The network ‘Scalable Advanced Ring-based passive Dense Access Network Architecture’ (SARDANA) based on this topology is presented and demonstrated. In the SARDANA network the interconnection between the ring and the trees is done by means of a special node, the remote node. This node is a fundamental element to the operation, resiliency and scalability of the network. This document presents and compares different topologies to the implementation of the remote node. Remotely reconfigurability of the remote nodes is also demonstrated by means of optical conversion and control modules. An important factor to the optimization of the remote nodes is the remote amplification done by means of erbium doped fibers being presented the analysis of the amplifier. Finally is demonstrated a prototype of a node remotely reconfigured and efficient

Architecture and communication protocol to monitor and control water quality and irrigation in agricultural environments

[ES] La introducción de soluciones tecnológicas en la agricultura permite reducir el uso de recursos y aumentar la producción de los cultivos. Además, la calidad del agua de regadío se puede monitorizar para asegurar la seguridad de los productos para el consumo humano. Sin embargo, la localización remota de la mayoría de los campos presenta un problema para proveer de cobertura inalámbrica a los nodos sensores y actuadores desplegados en los campos y los canales de agua para regadío. El trabajo presentado en esta tesis aborda el problema de habilitar la comunicación inalámbrica entre los dispositivos electrónicos desplegados para la monitorización de la calidad del agua y el campo a través de un protocolo de comunicación y arquitectura heterogéneos. La primera parte de esta tesis introduce los sistemas de agricultura de precisión (PA) y la importancia de la monitorización de la calidad del agua y el campo. Asimismo, las tecnologías que permiten la comunicación inalámbrica en sistemas PA y el uso de soluciones alternativas como el internet de las cosas bajo tierra (IoUT) y los vehículos aéreos no tripulados (UAV) se introducen también. Después, se realiza un análisis en profundidad del estado del arte respecto a los sensores para la monitorización del agua, el campo y las condiciones meteorológicas, así como sobre las tecnologías inalámbricas más empleadas en PA. Además, las tendencias actuales y los desafíos de los sistemas de internet de las cosas (IoT) para regadío, incluyendo las soluciones alternativas introducidas anteriormente, han sido abordados en detalle. A continuación, se presenta la arquitectura propuesta para el sistema, la cual incluye las áreas de interés para las actividades monitorización que incluye las áreas de los canales y el campo. A su vez, la descripción y los algoritmos de operación de los nodos sensores contemplados para cada área son proporcionados. El siguiente capítulo detalla el protocolo de comunicación heterogéneo propuesto, incluyendo los mensajes y alertas del sistema. Adicionalmente, se presenta una nueva topología de árbol para redes híbridas LoRa/WiFi multisalto. Las funcionalidades específicas adicionales concebidas para la arquitectura propuesta están descritas en el siguiente capítulo. Éstas incluyen algoritmos de agregación de datos para la topología propuesta, un esquema de las amenazas de seguridad para los sistemas PA, algoritmos de ahorro de energía y tolerancia a fallos, comunicación bajo tierra para IoUT y el uso de drones para adquisición de datos. Después, los resultados de las simulaciones para las soluciones propuestas anteriormente son presentados. Finalmente, se tratan las pruebas realizadas en entornos reales para el protocolo heterogéneo presentado, las diferentes estrategias de despliegue de los nodos empleados, el consumo energético y la función de cuantificación de fruta. Estas pruebas demuestran la validez de la arquitectura y protocolo de comunicación heterogéneos que se han propuesto.[CA] La introducció de solucions tecnològiques en l'agricultura permet reduir l'ús de recursos i augmentar la producció dels cultius. A més, la qualitat de l'aigua de regadiu es pot monitoritzar per assegurar la qualitat dels productes per al consum humà. No obstant això, la localització remota de la majoria dels camps presenta un problema per a proveir de cobertura sense fils als nodes sensors i actuadors desplegats als camps i els canals d'aigua per a regadiu. El treball presentat en aquesta tesi tracta el problema d'habilitar la comunicació sense fils entre els dispositius electrònics desplegats per a la monitorització de la qualitat de l'aigua i el camp a través d'un protocol de comunicació i arquitectura heterogenis. La primera part d'aquesta tesi introdueix els sistemes d'agricultura de precisió (PA) i la importància de la monitorització de la qualitat de l'aigua i el camp. Així mateix, també s'introdueixen les tecnologies que permeten la comunicació sense fils en sistemes PA i l'ús de solucions alternatives com l'Internet de les coses sota terra (IoUT) i els vehicles aeris no tripulats (UAV). Després, es realitza una anàlisi en profunditat de l'estat de l'art respecte als sensors per a la monitorització de l'aigua, el camp i les condicions meteorològiques, així com sobre les tecnologies sense fils més emprades en PA. S'aborden les tendències actuals i els reptes dels sistemes d'internet de les coses (IoT) per a regadiu, incloent les solucions alternatives introduïdes anteriorment. A continuació, es presenta l'arquitectura proposada per al sistema, on s'inclouen les àrees d'interès per a les activitats monitorització en els canals i el camp. Finalment, es proporciona la descripció i els algoritmes d'operació dels nodes sensors contemplats per a cada àrea. El següent capítol detalla el protocol de comunicació heterogeni proposat, així como el disseny del missatges i alertes que el sistema proposa. A més, es presenta una nova topologia d'arbre per a xarxes híbrides Lora/WiFi multi-salt. Les funcionalitats específiques addicionals concebudes per l'arquitectura proposada estan descrites en el següent capítol. Aquestes inclouen algoritmes d'agregació de dades per a la topologia proposta, un esquema de les alertes de seguretat per als sistemes PA, algoritmes d'estalvi d'energia i tolerància a fallades, comunicació per a IoUT i l'ús de drons per a adquisició de dades. Després, es presenten els resultats de les simulacions per a les solucions proposades. Finalment, es duen a terme les proves en entorns reals per al protocol heterogeni dissenyat. A més s'expliquen les diferents estratègies de desplegament dels nodes empleats, el consum energètic, així com, la funció de quantificació de fruita. Els resultats d'aquetes proves demostren la validesa de l'arquitectura i protocol de comunicació heterogenis propost en aquesta tesi.[EN] The introduction of technological solutions in agriculture allows reducing the use of resources and increasing the production of the crops. Furthermore, the quality of the water for irrigation can be monitored to ensure the safety of the produce for human consumption. However, the remote location of most fields presents a problem for providing wireless coverage to the sensing nodes and actuators deployed on the fields and the irrigation water canals. The work presented in this thesis addresses the problem of enabling wireless communication among the electronic devices deployed for water quality and field monitoring through a heterogeneous communication protocol and architecture. The first part of the dissertation introduces Precision Agriculture (PA) systems and the importance of water quality and field monitoring. In addition, the technologies that enable wireless communication in PA systems and the use of alternative solutions such as Internet of Underground Things (IoUT) and Unmanned Aerial Vehicles (UAV) are introduced as well. Then, an in-depth analysis on the state of the art regarding the sensors for water, field and meteorology monitoring and the most utilized wireless technologies in PA is performed. Furthermore, the current trends and challenges for Internet of Things (IoT) irrigation systems, including the alternate solutions previously introduced, have been discussed in detail. Then, the architecture for the proposed system is presented, which includes the areas of interest for the monitoring activities comprised of the canal and field areas. Moreover, the description and operation algorithms of the sensor nodes contemplated for each area is provided. The next chapter details the proposed heterogeneous communication protocol including the messages and alerts of the system. Additionally, a new tree topology for hybrid LoRa/WiFi multi-hop networks is presented. The specific additional functionalities intended for the proposed architecture are described in the following chapter. It includes data aggregation algorithms for the proposed topology, an overview on the security threats of PA systems, energy-saving and fault-tolerance algorithms, underground communication for IoUT, and the use of drones for data acquisition. Then, the simulation results for the solutions previously proposed are presented. Finally, the tests performed in real environments for the presented heterogeneous protocol, the different deployment strategies for the utilized nodes, the energy consumption, and a functionality for fruit quantification are discussed. These tests demonstrate the validity of the proposed heterogeneous architecture and communication protocol.García García, L. (2021). Architecture and communication protocol to monitor and control water quality and irrigation in agricultural environments [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17422

Modeling water availability for smallholder farming in inland valleys under climate and land use / land cover change in Dano, Burkina Faso

Effective water management in inland valley catchments is crucial for adaptation to the adverse impact of climate change and land use and land cover change (LULCC) on smallholder farming systems, poverty reduction, attaining food security, and ecosystem preservations in the West African region. An intensive hydrological instrumentation of four sparse data catchments (Bankandi-Loffing, Mebar, Moutori, and Fafo in Dano, Burkina Faso) has been undertaken in order to better understand hydrological processes which control water availability, to calibrate and validate the physically-based and spatially distributed water balance simulation model WaSiM, to assess the impact of climate and land use and land cover change on water resources, and subsequently to derive strategies for improving the capacity of smallholder farmers to cope with water scarcity and climate variabilities. The instrumentation of the catchment helped to achieve three years (2014-2016) of high temporal and spatial resolution data. The temporal resolutions of meteorological and stream flow data were 5 min to 10 min, six hours to a week for piezometric data, and 30 min to a week for soil moisture data. Five rain recorders, seven stream gauges, 64 piezometers in shallow groundwater (2). Additionally, the groundwater tables of three relatively deep wells (6 m, 16 m, and 25 m deep) were monitored. The analyses of hydrographs and the flow duration curves (FDC) using observed discharge show less discharge in the headwater sub-catchments compared to the downstream sub-catchments. This is due to the low contribution of base flow in the headwater sub-catchments. The decomposition of total runoff using observed hydrographs and stream electric conductivity suggests that interflow is the major contributor to total discharge. The calibration and validation of the Bankandi-Loffing catchment achieved a good model performance using the coefficient of determination (R2), the Nash-Sutcliffe efficiency (NSE), the Kling-Gupta efficiency (KGE), and the percent bias (Pbias). The R2 ranges from 0.47 to 0.95, NSE from 0.40 to 0.95, and KGE from 0.57 to 0.84 between the observed and simulated discharge. The numerical performance for soil moisture modeling is 0.70 for both R2 and NSE, and 0.80 for KGE while for the groundwater table modeling the results are 0.30, 0.20, and 0.5 for R2, NSE, and KGE, respectively. The fact that the transfer of the parameter set from Bankandi-Loffing to Mebar catchment without recalibration resulted in a good model performance (R2: 0.93, NSE: 0.92, and KGE: 0.84 in 2014-2015; R2: 0.65, NSE: 0.64, and KGE: 0.59) suggests the strong robustness of WaSiM in the investigated area. The resulting water balance shows that evapotranspiration is quantitatively the most important hydrological process, physical evaporation dominates the evapotranspiration, and 14% of rainfall runs out of the catchment as discharge. Interflow dominates runoff at the headwater sub-catchments whereas base flow is the major runoff component in the downstream area where the inland valley bottoms are located. The conversion of savanna to cropland leads to an increase of surface runoff. This is potentially associated with an exacerbation of soil erosion and soil fertility loss. Therefore, supplementing the current erosion technique (stone-belt) with agroforestry and/or mulching will reduce the negative effects of land cover change. Two scenarios were considered during the impact assessment. The first scenario evaluated exclusively the climate change impact by utilizing five regional climate models (RCMs) using land use and land cover (LULC) of the year 2013 for both the reference period (1971-2000) and the projection period (2021-2050). Each RCM is composed of the representative concentration pathways (RCPs) 4.5 and 8.5. The results indicate large uncertainty in the discharge projection for the future. Three RCMs predict an increase of total runoff for the projection period compared to the reference period. The mean total runoff increase is +61% (standard deviation Std= 31%) compared to the reference period. However, two RCMs project a decrease of total runoff. The mean total runoff decrease is -34% (Std= 10%) compared to the reference period. The second scenario utilizes the five RCMs and LULC 2013 for the reference period and LULC 2030 for the projection period in order to assess the combined impact of climate change and LULCC. The results suggest that LULCC exacerbates the increase of total runoff in combination with the three RCMs with a mean increase in total runoff by +108% (Std= 38%) compared to the reference period (versus mean= +61% in the first scenario). However, for the two RCMs predicting a decrease of total runoff, LULCC reduces the decrease of total runoff. The mean decrease is -20% (Std= 10%) compared to the reference period (versus mean= -34% in the first scenario). The results of this study can be used as input to water management models in order to derive strategies to cope with present and future water scarcities for smallholder farming in the investigated area.Modélisation de la disponibilité de l'eau pour les petites exploitations agricoles des bas-fonds sous l’influence du changement climatique, d’utilisation des sols / couverture végétale à Dano, Burkina Faso La gestion efficiente des ressources en eau dans les bassins versants des bas-fonds est indispensable non seulement pour l’adaptation aux impacts néfastes du changement climatique, utilisation sols / couverture végétale sur les petites exploitations agricoles, mais aussi pour réduire la pauvreté, l’insécurité alimentaire et préserver les écosystèmes en Afrique de l’Ouest. Une instrumentation hydrologique intensive de quatre (04) bassins versants pourvus de très peu de données (Bankandi-Loffing, Mebar, Moutori et Fafo situés à Dano, Burkina Faso) a été entreprise afin de mieux comprendre les processus hydrologiques qui contrôlent la disponibilité en ressources hydrologiques. Le modèle WaSiM (modèle à base physique distribué) a été utilisé, pour évaluer les impacts du changement climatique, d’utilisation des sols et de couverture végétale sur les ressources en eau. Cette étude pourra aider à développer des stratégies d’amélioration de la capacité des petits exploitants agricoles à surmonter les problèmes de manque d’eau et de variabilités climatiques. L'équipement hydrologique des bassins versants a permis d'obtenir durant trois (03) années (2014-2016) de données de hautes précisions temporelles et spatiales. Les précisions temporelles des données météorologiques et des données de débit des cours d'eau étaient de 5 à 10 minutes. Ces précisions étaient de 6 heures à une semaine pour les données piézométriques et de 30 minutes et une semaine pour les données sur l'humidité du sol. Cinq (05) pluviomètres, sept (07) station limnimétriques, soixante-quatre (64) piézomètres captant la nappe phréatique (< 5 m de profondeur), soixante-quatre (64) points de mesures de l'humidité du sol à trois profondeurs (5 cm, 30 cm et 50 cm) ont été installés et rendus opérationnels sur les quatre bassins versants (leur superficie total est d’environ 65 km2;). De plus, le niveau de la nappe phréatique a été régulièrement mesuré dans trois puits relativement profonds (6 m, 16 m et 25 m de profondeurs respectivement). Les analyses des hydrogrammes et des courbes de débits classés à partir des débits observés révèlent des débits plus faibles dans les sous-bassins en amont par rapport aux sous-bassins en aval. Cela s’explique en partie par la faible contribution des écoulements de base dans les sous-bassins en amont. La décomposition de l’écoulement à l'aide des hydrogrammes de débits observés et de la conductivité électrique des cours d'eau suggère que l'écoulement hypodermique est le principal contributeur des écoulements. La calibration et la validation de WaSiM pour le bassin versant de Bankandi-Loffing ont permis d'obtenir une bonne performance du modèle en utilisant le coefficient de détermination (R2), l'efficacité de Nash-Sutcliffe (NSE), l'efficacité de Kling-Gupta (KGE), et le pourcentage de biais (Pbias). R2 varie de 0,47 à 0,95, NSE de 0,40 à 0,95 et KGE de 0,57 à 0,84 entre les débits observés et les débits simulés. La performance numérique pour la modélisation de l'humidité du sol est de 0,70 pour les deux paramètres de performance R2 et NSE, et de 0,80 pour KGE. Concernant la modélisation du niveau de la nappe phréatique, les résultats sont de 0,30, 0,20 et 0,5 pour R2, NSE et KGE, respectivement. Le fait que le transfert du jeu de paramètres de Bankandi-Loffing au bassin versant de Mebar sans recalibration ait donné lieu à une bonne performance du modèle (R2: 0,93, NSE: 0,92, et KGE: 0,84 en 2014-2015 ; R2: 0,65, NSE: 0,64, et KGE: 0,59 en 2016) dénote une forte robustesse du modèle WaSiM pour la zone d’étude. Le bilan hydrique qui résulte de la modélisation montre que l'évapotranspiration est le processus hydrique le plus important quantitativement. L'évaporation physique est plus importante que la transpiration et 14% des précipitations s'écoulent du bassin versant sous forme d'écoulement de surface. Le ruissellement de surface domine les écoulements dans les sous-bassins en amont, tandis que l'écoulement de base est la principale composante des écoulements dans les sous-bassins en aval où se situent les bas-fonds. La conversion des savanes en terres cultivées entraîne une augmentation du ruissellement de surface. Ceci est potentiellement associé à une exacerbation de l'érosion et à la perte de fertilité des sols. Par conséquent, il serait envisageable de compléter les techniques anti-érosives actuelles (ceinture de pierres) par de l'agroforesterie et/ou du paillage. Deux scénarii ont été considérés lors de l’étude d'impact. Le premier scénario a évalué uniquement l'impact du changement climatique en se servant de cinq (05) modèles climatiques régionaux (RCMs) et de la carte d’utilisation des sols / couverture végétale de l'année 2013 (LULC 2013) pour la période de référence (1971-2000) et pour les projections futures (2021-2050). Chaque RCM est composé de profils représentatifs d’évolution des concentrations (RCPs) 4.5 et 8.5.  Les résultats indiquent une grande incertitude des projections de débits d’écoulement pour l'avenir. Trois RCMs prévoient une augmentation moyenne annuelle de débits de +61% (écart-type Std = 31%) par rapport à la période de référence. En revanche deux RCMs prévoient une diminution des débits de -34% (Std = 10%) en moyenne par rapport à la période de référence. Le deuxième scénario a utilisé les cinq RCMs et le LULC 2013 pour la période de référence et le LULC 2030 pour le futur afin d'évaluer l'impact combiné du changement climatique et de le LULCC. Les résultats suggèrent que le LULCC accentue l'augmentation des débits quand il est combiné avec les trois modèles prévoyant l’augmentation des débits. L'augmentation moyenne des débits est de +108% (Std = 38%) par rapport à la période de référence (contre +61% en moyenne dans le premier scénario). Cependant, pour les deux RCMs qui prévoient une diminution des débits, le LULCC attenue le changement de débit. La diminution moyenne de débit est de -20% (Std = 10%) par rapport à la période de référence (contre –34% en moyenne dans le premier scénario). Les résultats de cette étude pourront servir de données d’entrée aux modèles de gestion des ressources en eau afin d’élaborer des stratégies pour faire face aux pénuries d’eau actuelles et futures pour les petites exploitations agricoles dans la zone d’étude

Towards Real-World Adoption of Quantum Key Distribution using Entangled Photons

In order for quantum key distribution (QKD) to move from the lab to widespread adoption, it will need to be compatible with existing infrastructure. To that end, I demonstrate an implementation of QKD with entangled photons on active, standard telecommunications ber. By using a wavelength outside of the conventional band used by telecommunications tra c, I achieve minimal disruption to either the quantum or classical signals. In an attempt to extend the reach of QKD with entangled photons I studied the parameters of these systems. I developed a model for the number of measured two-fold coincidences that maximizes the secure key rate (SKR), for any combination of system parameters, using a symbolic regression algorithm based on simulated data. I validated this model against experimental data, and demonstrated its usefulness by applying it to simulations of QKD between the ground and a satellite and in optical bers. Finally, I worked on a step towards a new entangled photon source that is a hybrid between visible and telecommunications wavelengths by building a hybrid single photon source

Vegetation change detection and soil erosion risk assessment modelling in the Man River basin, Central India

Land use change directly increased soil erosion risk, which is a very sensitive environmental issue in Central India. To evaluate the response of land use changes on soil erosion risk, research was implemented using remote sensing techniques, coupled with ground information, to develop an integrated modelling approach to study the factors driving land use changes in the Man River basin, Central India. Results were used to assess the impact of land use change on soil erosion risk. First, a series of sub methods were applied to monitor and verify land use land cover change in the study area which included pre-processing, classification and assessment of land use transaction from 1971 to 2013 using Landsat time series imagery. Additionally, an independent spatial assessment of deforestation, forest degradation and responsible drivers for the period 2009-2013 was conducted to enable a deeper analysis of forestry activates using the GIS based direct interpretation approach. The research also developed a robust accuracy assessment method to check the quality of the 2009 and 2013 classification maps using good quality Google Earth TM imagery and a field measured GPS dataset. These approaches were largely based on the GOFC- GOLD (2010) and IPCC good recommendations for land use land cover mapping and verification. The information obtained from an accuracy assessment was also used to estimate deforestation area and construct confidence intervals that reflect the uncertainty of the area estimates obtained. Such analysis is rarely applied in current published verification assessments. In the second phase of the study, a Geo-spatial interface for process-based Water Erosion Prediction Project (GeoWEPP) was implemented, to estimate the response of land use and land cover change on soil erosion risk in several scenarios derived from both ground and satellite based precipitation, DEMs and vegetation change. GeoWEPP was used at the hillslope scale in three selected watersheds within the Man River basin using Landsat, LISSIII, Cartosat-1, ASTER, SRTM, TRMM and ground based datasets. The results highlight that the study developed a realistic approach using remote sensing techniques to understand the pattern and process of landscape change in the Man River basin and its response on soil erosion risk. Over the last four decades, forest and agriculture areas were found to be the most dynamic land use /land cover categories. During the last four decades, around 54200 ha (33.7 %) forest area has been decreased due to the expansion of agriculture, forest harvesting and infrastructure development. The direct interpretation approach estimated similar patterns of deforestation and forest degradation associated with iii drivers for the 2009 to 2013 time period, but this approach also provided more accurate and location specific information than automatic analysis. The overall correspondence between the map and reference data are a good measure for 2009 and 2013; 94.03 % and 92.8 % respectively. User‘s and producer‘s accuracies of individual classes range from 75 % to 99 %. Using the accuracy assessment data and a simple set of equations, an error-adjusted estimate of the area of deforestation was obtained (± 95% confidence interval) of 23382 ± 550 ha. The estimated average annual soil loss for all three watersheds is 21 T/ha which was found to be comparable to similar studies carried out in the study region. The highest soil loss rates occurred in areas of agriculture (301 T. /ha /yr) and fallow land (158 T/ha/yr), while the lowest rates were recorded in forest land (33.45 T/ha/yr). Agriculture extension (316.5 ha) due to forest harvesting (234 ha) in the last four decades is one of the significant drivers to speed up soil erosion (7.37 T/ha/yr.) in all three watersheds. The spatial pattern of erosion risk indicates that areas with forest cover have minimum rates of soil erosion, while areas with extensive human intervention such as agriculture and fallow land, have high estimated rates of soil erosion. The different DEMs generated varied topographic and hydrologic attributes, which in turn led to significantly different erosion simulations. GeoWEPP using Cartosat-1 (30 m) and SRTM (90 m) produced the most accurate estimation of soil loss which was close to similar already published studies in the area. TRMM rainfall data has good to use as a rainfall parameter for soil erosion risk mapping in study area. Overall, the integrated approach using remote sensing and GIS allowed a clear understanding of the factors that drive land use/land cover change to be developed and enabled the impact of this change on soil erosion risk in the Man River basin, Central India to be assessed

New Approaches in Engineering Somatic Embryogenesis in Loblolly Pine Suspension Cultures

Many industries including agriculture and healthcare require efficient methods for replication of plants with optimal traits. The loblolly pine (Pinus taeda) is a valuable crop in the timber industry, occupying 30 million acres of U.S. land, and breeding efforts aim to produce a crop with ideal phenotypic traits, including superior growth and wood quality. One method to large-scale clonal crop propagation is somatic embryogenesis (SE), the process through which asexual (somatic) plant cells undergo differentiation in vitro, resulting in germination-competent embryos. There are three main stages of growth and development that lead to the production of embryos: 1) aggregated cells that form embryonic suspensor masses (ESMs) are grown and scaled up in maintenance cultures; 2) ESMs are plated on solid media to initiate SE; and 3) embryos are separated from the ESM and germinated to generate plants. However, this process is not fundamentally understood, leading to large, unpredictable variability in embryo yield, a number only determined 8-12 weeks downstream of SE initiation. This work aims to glean fundamental insight into culture dynamics and correlations with outcomes while simultaneously providing engineering strategies to improve embryo yield. Here, a variety of process manipulations and their effects on SE process outcomes and performance are presented. Induction of stress-related pathways through exogenous addition of plant stress hormones prior to moving a culture into development was shown to improve the rate of SE, and this knowledge was used to explore a means for more efficient embryo production. A clear link between the total volume of small cell aggregates and embryo yield was demonstrated, enabling yield prediction at a timepoint 12 weeks before previously possible. Finally, methods for culture protein modification without genetic transformation were developed through inhibition or supplementation of endogenous extracellular arabinogalactan proteins (AGPs), which were found to significantly influence SE in loblolly pine. Techniques were developed to characterize the influence of these treatments on embryo yield as well as the molecular response of the cultures, including culture stress (determined by phenolic content), growth (using a Coulter counter), and total and specific protein biomarkers. The work presented here is among the first studies that consider process engineering as a simple and cost-effective means to improve the overall feasibility of SE on both an academic and industrial scale

Advanced materials, process, and designs for silicon photonic integration

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.Includes bibliographical references (p. 229-235).The copper (Cu) interconnect has become the bottleneck for bandwidth scaling due to its increasing RC time constant with the decreasing gate line width. Currently, silicon based optical interconnect is widely pursued as the most promising technology to replace Cu in microprocessor chips. Silicon optical interconnect is based on integrated silicon nanophotonic technologies. It can leverage the large scale and low cost of CMOS technology and deliver higher bandwidth with no EMI and low heat dissipation. Passive photonic component, such as waveguides, couplers, filters, splitters, are the backbone of integrated photonic circuit. This thesis is dedicated to the development of low loss, high performance, high index contrast optical waveguides and couplers via materials, processes engineering, development, and device designs. We primarily focus on SOI single crystalline silicon (c-Si or SOI), PECVD amorphous silicon (a-Si:H, or simplified as a-Si), and PECVD silicon nitride (SiNxHy) based single mode channel waveguides.We have previously identified that sidewall roughness scattering is the dominant loss mechanism for the TE mode in high index contrast single mode channel waveguides. In this thesis, we provide a comprehensive understanding of the roughness scattering and its positive correlations with (1) sidewall optical intensity; (2) sidewall RMS roughness; and (3) sidewall index contrast. Novel processes and designs, such as hard mask and chemical oxidation, are developed based on the above understanding. In single mode, 500 x 200 nm2 c-Si channel waveguides, we have achieved world-record 2.7 dB/cm and 0.7 dB/cm transmission loss coefficients for the TE mode and the TM mode, respectively.For deposited waveguides, bulk absorption loss is also important for both TE and TM modes.For PECVD a-Si, we adapt hydrogen passivation to reduce dangling bond density.(cont.) We also use a thin silicon nitride as the over cladding layer to help preserve H passivation and to reduce sidewall index contrast, acting as the graded index layer for a-Si waveguide core. We have accomplished the lowest reported loss coefficients in directly etched, single mode, 700 x 100 nm2 a-Si channel waveguides of 2.7 dB/cm for the TE mode, comparable to c-Si waveguide with similar dimensions. For the first time, damascene process has also been demonstrated as a promising process for a-Si waveguide fabrication. We have achieved a record-low loss of 2.5 dB/cm in 600 x 100 cm2 a-Si channel waveguides. Chemical-mechanical polishing (CMP) is the most critical step.For PECVD SiNxHy, we have previously identified that the absorption loss is due to the resonant absorption caused by N-H vibration. In this thesis, three different low temperature approaches have been developed and optimized to reduce NH concentration in as-deposited SiNxHY via (1) deposition chemistry; (2) post-deposition Ultraviolet light (UV) treatment; and (3) post-deposition, in-situ N2/Ar plasma treatment. All three processes are compatible with CMOS back-end processes, such as a-Si process. While changing deposition chemistry is the simplest method to obtain low NH containing SiNxHy, it comes with high SiH concentration and may have undesirable properties. Experimentally, for UV treatment, the highest H removal percentage is 60%; for plasma treatment, - 90%. UV treatment shows strong compositional dependence. The underlying mechanism of such dependence is identified and confirmed by Monte-Carlo modeling. Low loss and spectrally broadband optical couplers are indispensable optical components in an integrated photonic circuit. A high performance coupler should be capable of overcoming the mode-size mismatch, mode-shape mismatch, mode-position mismatch, and polarization mismatch, bridging different optical devices with minimal coupling loss. In this thesis, we have demonstrated a fiber-to-waveguide coupler based on asymmetric graded index taper and monolithically integrated cylindrical lens.(cont.) It is capable of transforming single mode light between single mode fiber and waveguides with minimal coupling loss of 0.45 dB between 1520 nm and 1630 nm. We have also demonstrated a vertical waveguide-to-waveguide coupler that is based on complementary inverse tapers. This design is tolerant of large refractive index mismatch between the two waveguides and also of any fabrication variation that would affect the effective indices of the two waveguides. We have achieved a minimal coupling loss of 0.25 dB per coupler and excellent broadband behavior is also demonstrated. Slot waveguides are a newly developed class of waveguides with unique optical properties. Slot waveguides can achieve exceptional high optical field in nanometer sized low index regions. In this thesis, we have demonstrated low loss transmission of 6 dB/cm for the fundamental slot mode in horizontal slot waveguides at 1550 nm. The horizontal slot configuration removes the constraints of thin slot definition by lithography and allows an arbitrarily thin slot to be fabricated via deposition or oxidation. Because the resulting interface is much smoother than the etched interface, the transmission loss in horizontal slot waveguides is much lower than in vertical slot waveguides. We also demonstrated that multiple slot configurations result in higher optical confinement compared to single slot configurations with the same slot thickness. The low loss and high optical confinement in the low index slot region realized in horizontal slot waveguides promises many useful applications, such as Er-doped silicon-based light emitters. For integration of slot waveguides with conventional channel waveguides, we have designed and simulated mode couplers and polarization rotators for slot-slot, slot-channel waveguide mode transformations.Athermal operation is important for realizing stable passive, WDM optical network on silicon. Athermal design of silicon waveguide systems uses advanced polymer cladding of large negative TO coefficient to provide compensation for the large positive TO coefficient in silicon. The reduced thermo-optic (TO) effect is experimentally demonstrated by reducing TO coefficient from 85 pm/K to 11 pm/K using polymer films.by Rong Sun.Ph.D

Contributions to hydraulic engineering.

Thesis (Ph.D.)-University of Natal, Durban, 1984.No abstract available