Dissertations / Theses on the topic 'Fog layer'

Clouds are powerful computer centers that provide computing and storage facilities that can be remotely accessed. The flexibility and cost-efficiency offered by clouds have made them very popular for business and web applications. The use of clouds is now being extended to safety-critical applications such as factories. However, cloud services do not provide time predictability which creates a hassle for such time-sensitive applications. Moreover, delays in the data communication between clouds and the devices the clouds control are unpredictable. Therefore, to increase predictability an intermediate layer between devices and the cloud is introduced. This layer, the Fog layer, aims to provide computational resources closer to the edge of the network. However, the fog computing paradigm relies on resource-constrained nodes, creating new potential challenges in resource management, scalability, and reliability. Solutions such as lightweight virtualization technologies can be leveraged for solving the dichotomy between performance and reliability in fog computing. In this context, container-based virtualization is a key technology providing lightweight virtualization for cloud computing that can be applied in fog computing as well. Such container-based technologies provide fault tolerance mechanisms that improve the reliability and availability of application execution.  By the study of a robotic use-case, we have realized that persistent data storage for stateful applications at the fog layer is particularly important. In addition, we identified the need to enhance the current container orchestration solution to fit fog applications executing in container-based architectures. In this thesis, we identify open challenges in achieving dependable fog platforms. Among these, we focus particularly on scalable, lightweight virtualization, auto-recovery, and re-integration solutions after failures in fog applications and nodes. We implement a testbed to deploy our use-case on a container-based fog platform and investigate the fulfillment of key dependability requirements. We enhance the architecture and identify the lack of persistent storage for stateful applications as an important impediment for the execution of control applications. We propose a solution for persistent fault-tolerant storage at the fog layer, which dissociates storage from applications to reduce application load and separates the concern of distributed storage. Our solution includes a replicated data structure supported by a consensus protocol that ensures distributed data consistency and fault tolerance in case of node failures. Finally, we use the UPPAAL verification tool to model and verify the fault tolerance and consistency of our solution.

The uncertainty in the determination of the momentum and scalar fluxes remains one of the main obstacles to accurate numerical forecasts in low to moderate wind conditions. For example, latent heat fluxes computed from data using direct covariance and bulk aerodynamic methods show that there is good agreement in unstable conditions when the latent heat flux values are generally positive. However, the agreement is relatively poor in stable conditions, particularly when the moisture flux is directed downward. If the direct covariance measurements are indeed accurate, then they clearly indicate that the bulk aerodynamic formula overestimate the downward moisture flux in stable conditions. As a result, comparisons of the Dalton number for unstable and stable conditions indicate a marked difference in value between the two stability regimes. Investigations done for this thesis used data taken primarily at the Air-Sea Interaction Tower (ASIT) during the Coupled Boundary Layers and Air-Sea Transfer (CBLAST) Experiment 2003 from the 20-27 August 2003. Other data from the shore based Martha's Vineyard Coastal Observatory (MVCO) and moored buoys in the vicinity of the ASIT were also incorporated. During this eight day period, the boundary layer was often characterized by light winds, a stably stratified surface layer and a swell dominated wave field. Additionally, the advection of warm moist air over cooler water resulted in fog formation and a downward flux of moisture on at least three occasions. Therefore, a primary objective of this thesis is to present a case study to investigate the cause of this shortcoming in the bulk formula under these conditions by examining the physical processes that are unique to these boundary layers. Particular attention will be paid to the behavior of the Dalton number in a stable marine atmospheric boundary layer under foggy conditions using insights derived from the study of fog formation and current flux parameterization methods.

La cellulosa è il polimero naturale più abbondante sulla terra, una risorsa rinnovabile che ogni anno viene prodotta in miliardi di tonnellate da molti organismi vegetali. Per questa ragione, su di essa si sta concentrando una crescente attenzione nell’ipotesi di una sua sempre maggiore applicazione nei più diversi campi. Quello del food packaging, che è ancora fortemente dipendente da materiali di sintesi e provenienti da risorse non rinnovabili, è particolarmente interessato ad un suo più ampio impiego, anche con il fine di aumentare la sostenibilità dei suoi prodotti e di ridurne l’impatto ambientale. Con questa tesi di dottorato si è inteso mettere a fuoco le potenzialità di impiego della nano cellulosa (cellulose nanocrystals, CNs), sperimentare la produzione e valutare le proprietà di alcune lacche a base di CNs, destinate a ricoprire convenzionali materiali flessibili per il confezionamento alimentare. La tesi si compone di quattro parti distinte. Nella prima parte si è inteso rappresentare lo stato dell’arte delle conoscenze e delle applicazioni della nanocellulosa, attraverso un ampio lavoro di documentazione bibliografica. Dapprima si è voluto mettere a fuoco quanto noto sulla struttura e la classificazione delle varie forme di nanocellulosa che è oggi possibile produrre e, a proposito della cellulosa nanocristallina in particolare, si è fatto il punto sulle tecniche di preparazione, la morfologia e le principali applicazioni. Da questo lavoro di documentazione sono emerse le notevoli proprietà di barriera ai gas ed a potenziali migranti, le eccellenti proprietà meccaniche (resistenza alla rottura, massima elongazione tensile, modulo di Young) e le interessanti caratteristiche termiche (transizione vetrosa, punto di fusione e di decomposizione) della CNs da sola ed in combinazione con altri materiali. Nella seconda sezione della tesi, al fine di comprendere meglio la struttura e la morfologia dei nanocristalli di cellulosa ottenuti attraverso un processo di idrolisi acida di linter di cotone, sono state utilizzate diverse tecniche analitiche avanzate, sia per la caratterizzazione qualitativa che quantitativa. E’ stato così possibile ottenere informazioni precise sulle dimensioni dei nano cristalli, il rapporto di forma, la solubilità e numerose altre loro importanti proprietà. In particolare le tecniche di TEM, SEM, e AFM sono apparse come le più adatte per osservare la morfologia dei cristalli, studiare le caratteristiche e la rugosità delle superfici trattate con lacche a base di CNs. Si è inoltre indagato sulla distribuzione delle dimensioni dei cristalli ottenuti e, grazie all’uso di FTIR, XPS e NMR, sulla natura dei gruppi funzionali disponibili e sulle loro interazioni. La terza parte della tesi è dedicata ad uno studio delle proprietà di alcuni differenti film, largamente impiegati per il food packaging (PET, OPP, OPA e cellophane), rivestiti con uno strato sottile di CNs. In particolare, è statomesso a punto il processo di laccatura e sono state misurate le proprietà ottiche (la trasparenza, l’opacità e le proprietà anti-fog), il coefficiente di frizione statico e dinamico, le energie superficiali e gli angoli di contatto, le proprietà di barriera all’ossigeno ed al vapor d’acqua. Da questo lavoro è emerso come sia effettivamente possibile rivestire di uno strato sottile (intorno ad un micron di spessore), omogeneo e continuo, film plastici differenti e che attraverso questo processo di laccatura, si riduce significativamente il coefficiente di frizione, si incrementano le proprietà anti-fog, si aumenta decisamente la barriera all’ossigeno, senza pregiudicare la trasparenza dei film di supporto. La prospettiva molto concreta è quella di costituire, in un modestissimo spessore, un coating multifunzionale con spiccate caratteristiche di sostenibilità e di sicurezza alimentare. L’ultima sezione della tesi è dedicata al lavoro fatto per sperimentare la possibile applicazione di una tecnica di rivestimento molto moderna (layer-by-layer coating, LbL) che sfrutta la formazione di legami elettrostatici tra biopolimeri caricati diversamente. In particolare si è dimostrata la possibilità di costituire lacche di un composito ottenuto mediante la sovrapposizione alternata di sottilissimi strati (da 6 a circa 30 nm) di chitosano e cellulosa nanocristallina. Il diverso pH delle soluzioni in cui vengono dispersi i due biopolimeri determina un diverso grado di ionizzazione delle cariche, rispettivamente positive del chitosano e negative della cellulosa, e di conseguenza diversi spessori e proporzioni relative dei due biopolimeri nel coating composito che si realizza. Ciò, evidentemente, permette di modulare in un ampio intervallo di valori, la permeabilità del film ricoperto. Il coefficiente di permeabilità del composito giunge a valori pari 0.02 cm3 µm m-2 24h-1 kPa-1, molto simili a quelli espressi da copolimeri a base di EVOH, in condizioni anidre. I vantaggi di un simile rivestimento sono comunque fondamentalmente legati alla sicurezza e non tossicità dei biopolimeri impiegati, dalla loro sostenibilità e dall’ampio grado di libertà disponibile nel modulare le caratteristiche finali di barriera, secondo le esigenze del prodotto da confezionare. Lo strato di lacca LbL così costituita rappresenta, in definitiva, una barriera all’ossigeno particolarmente promettente negli impieghi reali più critici anche per la concreta possibilità di realizzarla convenientemente su oggetti tridimensionali come bottiglie, vassoi e altri imballaggi finiti. In conclusione, le ricerche condotte rappresentano una base di partenza molto promettente per un’innovazione di sostenibilità e di prestazioni nel campo dell’imballaggio flessibile e meritano ulteriori approfondimenti ed applicazioni.
Being cellulose the most abundant natural polymer in biosphere, more and more attention has been paid on its new functionalities, sustainability, and renewability. Meanwhile, food packaging materials is one of the largest products we are using in daily life, but most of conventional materials are still oil-based due to their low cost and good performances. Therefore, in order to improve the sustainability and renewability of food packaging materials, this PhD dissertation focuses on development new nano-material (cellulose nanocrystals, CNs) for food packaging and includes mainly four sections. In the first section of this PhD dissertation, we reviewed the progress in knowledge on nano-cellulose first and then, specifically, on CNs. In this section the structure and classifications of various nano-cellulose preparations are included, as well as the preparation, the morphologies, and applications of CNs. In CNs applications, we reviewed that it exhibits excellent barrier, mechanical, and thermal properties itself or combined with other polymers. Particularly, the barrier properties refer to oxygen, water vapor, and migration barrier; mechanical properties are related with tensile strength, Young’s modulus, and strain percentage; the thermal properties include glass transition and melting or decomposition temperature, heat flow, and thermal mechanical parameters. In the second section of this PhD dissertation, to better understand the structure and status of CNs itself or in other polymers, we have used different powerful analytical tools for qualification and quantification. Firstly, we have obtained the relatively precise dimensions of CNs and observe its redispersability in different solvents, mainly water solutions. In the following, we could gain the information of the CNs status in other polymers in order to interpret the final performance efficiently. Finally, we preliminarily concluded that TEM, SEM, and AFM are suitable tools for observing individual crystals, estimating the roughness, and learning the morphology in different scale, respectively. As for the size distribution, functional groups, and interactions between the atoms of CNs, the particle size distributor, FTIR, XPS, and NMR are used for determinations, respectively. In the third section of this PhD dissertation, we have systematically investigated the properties of conventional films coated with CNs. In particular, we have analyzed their optical properties (transparency and haze), mechanical properties (static and dynamic coefficient of friction), anti-fog (contact angle and surface energy) and barrier properties (oxygen and water vapor transmission rates). In doing this, we have demonstrated that CNs coatings mainly lead to a reduction of friction, a premium feature for industrial applications, and that their influence on the optical properties of the packaging is not significant. Excellent anti-fog property guarantees customers more conveniently to evaluate the product inside the packages easily. At last but not the least, CNs coatings dramatically improve not only the oxygen barrier properties of conventional flexible food packaging, but also lead to a certain reduction in the water vapor transmission rate. The perspective use of CNs as multi-functional coatings favors a reduction of the required thickness for plastic films, towards a more environmentally-friendly and sustainable approach to packaging. In the last section of this PhD dissertation, we demonstrated the use of chitosan (CS)/CNs nanocomposites realized by layer-by-layer (LbL) self-assembly as oxygen barrier under different pH combinations. The oxygen permeability coefficient of CS/CNs nanocomposites is as low as 0.02 cm3 µm m-2 24h-1 kPa-1, close to EVOH co-polymers, under dry conditions. Meanwhile, we consider that CNs has no potential risks for human beings and the renewable origin of the carbohydrate polymers as significant added values that justify a deeper investigation. Finally, it deserves to be underlined also the chance of finely tuning the oxygen permeability by means of the pH values and the sharp control of the thickness associated with this process. Therefore, based on the advantages outlined above, the LbL CS/CNs nanocomposite represents a promising oxygen barrier component in transparent flexible packaging materials and semi rigid tridimensional objects (bottles, trays, boxes and etc.). Based on our researches, we conclude that CNs leads to very promising applications in food packaging field and deserves to be further investigated in the future.

Thesis (S.M.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 2005.
Includes bibliographical references (leaves 70-72).
The uncertainty in the determination of the momentum and scalar fluxes remains one of the main obstacles to accurate numerical forecasts in low to moderate wind conditions. For example, latent heat fluxes computed from data using direct covariance and bulk aerodynamic methods show that there is good agreement in unstable conditions when the latent heat flux values are generally positive. However, the agreement is relatively poor in stable conditions, particularly when the moisture flux is directed downward. If the direct covariance measurements are indeed accurate, then they clearly indicate that the bulk aerodynamic formula overestimate the downward moisture flux in stable conditions. As a result, comparisons of the Dalton number for unstable and stable conditions indicate a marked difference in value between the two stability regimes. Investigations done for this thesis used data taken primarily at the Air-Sea Interaction Tower (ASIT) during the Coupled Boundary Layers and Air-Sea Transfer (CBLAST) Experiment 2003 from the 20-27 August 2003. Other data from the shore based Martha's Vineyard Coastal Observatory (MVCO) and moored buoys in the vicinity of the ASIT were also incorporated.
(cont.) During this eight day period, the boundary layer was often characterized by light winds, a stably stratified surface layer and a swell dominated wave field. Additionally, the advection of warm moist air over cooler water resulted in fog formation and a downward flux of moisture on at least three occasions. Therefore, a primary objective of this thesis is to present a case study to investigate the cause of this shortcoming in the bulk formula under these conditions by examining the physical processes that are unique to these boundary layers. Particular attention will be paid to the behavior of the Dalton number in a stable marine atmospheric boundary layer under foggy conditions using insights derived from the study of fog formation and current flux parameterization methods.
by Robert Farrington Crofoot.
S.M.

Le brouillard est un phénomène météorologique très difficile à prévoir, même à très courte échéance, en raison de sa grande variabilité spatiale et temporelle qui est due à des interactions complexes entre divers processus physiques. Dans cette thèse, les caractéristiques météorologiques locales et les processus synoptiques favorables aux brouillards sur la région du Grand Casablanca (Maroc) sont examinés à l'aide des observations horaires aux deux stations météorologiques permanentes de cette région côtière. Un algorithme de classification objectif est développé et utilisé pour classer les événements en des types de brouillard les plus rencontrés. Cette étude climatologique a mis en évidence que le brouillard a le plus souvent un caractère localisé et que le type d'advection-rayonnement est le plus fréquent sur la région, suivi des types d'affaissement de stratus et de rayonnement. Quand le brouillard intéresse simultanément les deux stations, la probabilité d'observer deux types différents est assez élevée. Les processus advectifs liés à la circulation de brise de mer au cours de l'après-midi, suivis de ceux radiatifs en début de nuit jouent un rôle important dans la formation du brouillard sur la région. Des simulations numériques à l'aide du modèle Méso-NH sont réalisées. Ces simulations ont confirmé que les processus physiques impliqués dans le cycle de vie du brouillard peuvent être différents selon la nature géographique de la surface. Elles ont aussi mis en évidence que la prévision numérique du brouillard en zone côtière est sensible à la température de la surface de la mer, à la topographie locale, et à l'occupation du sol. De plus, la prévision du brouillard côtier dépend fortement de la capacité du modèle à reproduire correctement la circulation de brise au cours de l'après-midi et les processus radiatifs en début de nuit. Les simulations systématiques des cas de brouillard de l'hiver 2013-2014 a montré la capacité du modèle Méso- NH à reproduire l'occurrence du brouillard avec néanmoins un taux relativement élevé de fausses alarmes, en particulier à la station côtière
The prediction of fog remains a challenge due to its time and space variability and to the complex interaction between the numerous physical processes influencing its life cycle. During the first stage of this thesis, the local meteorological and synoptic characteristics of fog occurrence over the Grand Casablanca region (Morocco) are investigated. To achieve this, hourly surface meteorological observations, at two synoptic stations of this coastal region, are used. An objective fog-type classification has been developed in this work and used to discriminate the fog events into the well known types. This fog climatology points out that the fog is often localized and that it is predominantly of advection-radiation type, followed by fog resulting from cloud base lowering and radiation fog. Besides, two different fog types can occur when fog simultaneously concerns the two stations. The advective processes associated with sea breeze circulation during the daylight, followed by the radiative processes often leads to fog formation over this coastal region. Numerical simulations are performed later using the meso-scale non-hydrostatic model Meso-NH. These simulations confirm that the physical processes, governing the life cycle of fog, can be different according to the physiographic features of the area. Moreover, the numerical prediction of coastal fog over heterogeneous area is very sensitive to sea surface temperature, land local topography and land cover. It also depends on the model's ability to reproduce the sea breeze circulation during the daylight followed by the radiative processes early in the night. The systematic numerical simulations of the fog events that occurred during the winter 2013-2014 indicate the Meso-NH's ability to well capture the fog occurrence with a relatively high false alarm rate, particularly over the coastal station

Le travail presente est centre sur la situation ou l'effet radiatif des aerosols modifie la structure de la couche limite atmospherique. Trois situations sont etudiees: le cas des brumes seches, le cas des aerosols urbains et la cas du brouillard. La simulation numerique et l'approche experimentale conduisent au developpement ou la mise au point de programmes de calcul du transfert radiatif

In this work the application of ALD deposited SnOx films as electron transport layers in perovskite solar cells is analysed. Processes to fabricate homogeneous, transparent and conductive tin oxide films were developed on an Oxford Instruments FlexAL tool using a TDMASn precursor and H2O as oxidiser. Two process regimes were investigated; an ALD regime, where the precursor gases are fully separated by long purging steps and a pulsed-CVD regime, where short purge times allow for continuous reactions. Both process regimes were analysed at deposition temperatures from 100 – 250°C and showed a decrease in growth rate with an increase in refractive index for higher temperatures. In terms, of optical properties highly transparent films in the visible range (> 80%) were obtained for all analysed processes. The samples with the lowest absorption were SnOx films deposited at low temperatures in the pulsed-CVD regime. Films with low absorption also exhibited improved conductivity in the range of 200 – 500 Ωcm, which decreased further when the samples were heated. All investigated films were amorphous with a tin rich atomic composition of SnOx. The processes were performed to be compatible with n-i-p and inverted perovskite single junction solar cells as well as tandem devices on textured silicon bottom cells, due to conformal coating at low deposition temperatures and no need for thermal annealing steps. For the application on cell level, perovskite single junction solar cells in a n-i-p architecture were fabricated with a ~15 nm SnOx film as electron transport layer. To improve electron extraction properties different organic interlayers and mesoporous TiO2 were investigated below the perovskite absorber. It was seen that the use of PCBM on top of SnOx improved the solar cell performance of devices with a co-evaporated MAPbI3 absorber. Solar cells with efficiencies close to 6% were fabricated which exhibited a moderately high Voc of ~990 mV but low Jsc of < 10 mA/cm². For devices with wet-chemically deposited perovskite absorber materials, the fullerene solutions did not form a closed film due to wettability issues on SnOx and the risk of washing away by the spin-coated perovskite solution. SEM-images confirmed that no closed interlayers were formed in the wet-chemical devices which could be the cause of poor reproducibility for devices with a planar structure and SnOx as electron contact. The best performing device was achieved with SnOx and mesoporous TiO2 deposited by spin-coating and a MAPbI3 absorber. It showed a mean PCE from forward and reverse scans of 12.8% with a Voc > 990 mV and a Jsc close to 20 mA/cm². Compared to the TiO2 reference cells the devices using SnOx showed lower efficiencies but improved reproducibility and reduced hysteresis in the mesoporous structure. The produced cells serve as an initial proof of concept for the use of SnOx by ALD in the analysed solar cell structure.  To analyse the potential for commercialisation of perovskite based photovoltaic technologies a techno-economic analysis was performed. Taking into account up-scaled manufacturing processes for perovskite modules, manufacturing costs of 21.0 $/m² were calculated. This cost is below the calculated allowed extra costs for the top cell of a tandem device with 30 % efficiency, estimated at 30 – 80 $/m². Projections of the LCOE showed that perovskite single junction cells with a PCE of 15% and a lifetime of 25 years could achieve an LCOE of 5.2 c/kWh. For two-terminal tandem devices with a similar lifetime and an efficiency of 27% an LCOE of 6.6 c/kWh could potentially be achieved, making both technologies competitive with conventional energy technologies in Germany. An overview of literature on life cycle assessments showed that despite the use of lead based absorber materials, perovskite technologies have a minor environmental impact and are considered more sustainable than other photovoltaic technologies.
A I detta arbete appliceringen av ALD deponerade SnOx lager som selektiv kontakt till elektronerna perovskite solceller är analyserad. Processer för att fabricera homogena, transparenta och ledande SnOx lager utvecklades med en Oxford Instruments FlexAL med användnig av TDMASn gas och H2O. Två typer av processer analyserades; en ALD process, där dem reaktiva gaser är helt sepererade av långa rensande steg och en pulsed-CVD process, där korta rensningstider tillåter kontinuerliga reaktioner. Båda processer analyserades vid despositionstemperaturer från 100 till 250°C och visade en minsknig i tillväxtakten med en ökning i refractive index för högre temperaturer. Gällande optiska egenskaper, väldigt transparenta lager i det synliga området (> 80%) blev erhållna för alla analyserade processer. De proven med den lägsta absorptionen var SnOx filmer vid låga temperaturer i pulsed – CDV regimer. Lager med en låg absorption uppvisade ochså förbättrad ledningsförmåga inom intervaller från 200 – 500 Ωcm, som minskade ännu mer när proven blev uppvärmda. Alla utrettade lager var amorfisk med en hög andel tenn i SnOx. Procceserna genomfördes för att vara kompatibel med n-i-p och p-i-n perovskite solceller samt tandem apparater på texturerad kisel bottenceller, på grund av enhetlig beläggning vid låga depositionstemperaturer och inget behov av termisk behandling i efterhand. För applikationen på cellnivå, perovskite solceller i en n-i-p konstruktion tillverkades med ett ~15 nm SnOx  lager som selektiv kontakt till elektronerna. För att förbättra kontakten olika naturliga mellanskikter och mesoporös TiO2 undersöktes under det perovskite lagret. Det sågs att användnigen av PCBM på SnOx förbättrade funktionen av solcellerna av apparater med en dunstad MAPbI3 absorbator. Solceller med effektivitet nära 6% tillverkades, som ledde till en medelmåttligt hög Voc vid ~990 mV men låg Jsc vid < 10 mA/cm². För apparater med perovskite deponerade vid spin-coating, fullerene-lösningen bildade inget stängt lager på grund av vätningsproblem på SnOx och risken att tvätta bort den spin-coated perovskite lösningen. SEM-bilder bekräftade att inga stängda mellanskikter bildades i dem våtkemiska apparater. Det skulle kunna vara grunden till den dåliga reproducerbarheten av apparater med  en platt struktur och SnOx som selektiv kontakt till elektronerna. Den apparaten som uppträdde bäst uppnåddes med SnOx och mesoporös TiO2 deponerade vid spin-coating och en MAPbI3 absorbator. Det visade en genomsnittlig verkningsgrad av 12,8% med Voc > 990 mV och Jsc nära 20 mA/cm². I jämförelse med TiO2 referensceller, dem apparatener som använde SnOx visade lägra effektivitet men förbättrat reproducerbarhet och minskad hysteresis i den mesoporösa strukturen. Dem producerade celler tjäna som första bevis av konceptet för användningen av SnOx vid ALD i den analyserade strukturen av solcellerna.  För att analysera potentialen av kommersialiseringen av perovskite baserade photovoltaiv tekniker en ekonomisk analys genomfördes. Att ta med i beräkning storskalig tillverkningsprocesser till perovskite moduler, tillverkningskostnader vid 21.0 $/m² kalkulerades. Denna kostnad är under dem kalkulerade tillåtna extra kostnader till toppcellen av en tandem apparat med 30% effektivitet, beräknad vid 30 – 80 $/m². Projektioner av LCOE visade att perovskite celler med en verkningsgrad vid 15% och en livstid på 25 år skulle kunna uppnå ett LCOE vid 5.2 c/kWh. Två-terminal tandem apparater men en liknande livstid och en effektivitet vid 27% ett LCOE vid 6.6 c/kWh skulle potentiellt kunna bli uppnått, om man gjorde båda tekniker konkurrenskraftiga med andra energitekniker i Tyskland. En översikt av litteratur om livscykelanalyser visade att, trots användningen av blybaserad absorbtionsmaterial, perovskite tekniker har en låg miljöpåverkan och anses vara mer hållbart än andra foltovoltaisk tekniker.

In the article the results of analyze of laser ultrasound generation in inhomogeneous semiconductors plate is presented. The case of strong absorption of electromagnetic fields is considered. It is shown that in this case submicron surface layer thermal properties influence on thermal distribution evolution. The case of thin infinite plate considered. Peculiarities of excitation and propagation of elastic waves in such media regarding gives the possibility to obtain dispersive equation for laser ultrasound wave-vectors. It is shown that such processes in 1D case can be described. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35156

Cost-effective machining of hardened steel (>60 HRC) components such as a large wind turbine bearing poses a significant challenge. This thesis investigates a new laser tempering based hybrid turning approach to machine hardened AISI 52100 steel parts more efficiently and cost effectively. The approach consists of a two step process involving laser tempering of the hardened workpiece surface followed by conventional machining at higher material removal rates using lower cost ceramic tooling to efficiently cut the laser tempered material. The specific objectives of this work are to: (a) study the characteristics of laser tempering of hyper-eutectoid 52100 hardened steel, (b) model the laser tempering process to determine the resulting hardness, and (c) conduct machining experiments to evaluate the performance of the laser tempering based hybrid turning process in terms of forces, tools wear and surface finish. First, the microstructure alterations and phase content in the surface and subsurface layers are analyzed using metallography and x-ray diffraction (XRD) respectively. Laser tempering produces distinct regions consisting of - a tempered white layer and a dark layer- in the heat affected subsurface region of the workpiece. The depth of the tempered region is dependent on the laser scanning conditions. Larger overlap of laser scans and smaller scan speeds produce a thicker tempered region. Furthermore, the tempered region is composed of ferrite and martensite and weak traces of retained austenite (~ 1 %). Second, a laser tempering model consisting of a three dimensional analytical model to predict the temperature field generated by laser scanning of 52100 hardened steel and a phase change based hardness model to predict the hardness of the tempered region are developed. The thermal model is used to evaluate the temperature field induced in the subsurface region due to the thermal cycles produced by the laser scanning step. The computed temperature histories are then fed to the phase change model to predict the surface and subsurface hardness. The laser tempering model is used to select the laser scanning conditions that yield the desired hardness reduction at the maximum depth. This model is verified through laser scanning experiments wherein the hardness changes are compared with model predictions. The model is shown to yield predictions that are within 20 % of the measured hardness of the tempered region. Using the laser scanning parameters determined from the laser tempering model, cutting experiments using Cubic Boron Nitride (CBN) tools and low cost alumina ceramic tools are conducted to compare the performance of laser tempering based hybrid turning with the conventional hard turning process. The machining experiments demonstrate the possibility of higher material removal rates, lower cutting forces, improved tool wear behavior, and consequently improved tool life in the laser tempering based process. In addition, the laser tempered based hybrid turning process produce is shown to yield lower peak-to-valley surface roughness height than the conventional hard turning process. Furthermore, it is found that lower cost ceramic tools can be used in place of CBN tools without compromising the material removal rate.

>Magister Scientiae - MSc
Perovskite solar cells have attracted a tremendous amount of research interest in the scientific community recently, owing to their remarkable performance reaching up to 22% power conversion efficiency (PCE) in merely 6 to 7 years of development. Numerous advantages such as reduced price of raw materials, ease of fabrication and so on, have contributed to their increased popularity.

The aim of this thesis is to provide an in-depth investigation of zinc tin oxide, Zn1-xSnxOy or ZTO, grown by atomic layer deposition (ALD) as a buffer layer in Cu(In,Ga)Se2 (CIGS) solar cells. The thesis analyzes how changes in the ALD process influence the material properties of ZTO, and how these in turn affect the performance of CIGS solar cells. It is shown that ZTO grows uniformly and conformably on CIGS and that the interface between ZTO and CIGS is sharp with little or no interdiffusion between the layers. The band gap and conduction band energy level of ZTO are dependent both on the [Sn]/([Zn]+[Sn]) composition and on the deposition temperature. The influence by changes in composition is non-trivial, and the highest band gap and conduction band energy level are obtained at a [Sn]/([Zn]+[Sn]) composition of 0.2 at 120  °C. An increase in optical band gap is observed at decreasing deposition temperatures and is associated with quantum confinement effects caused by a decrease in crystallite size. The ability to change the conduction band energy level of ZTO enables the formation of suitable conduction band offsets between ZTO and CIGS with varying Ga-content. It is found that 15 nm thin ZTO buffer layers are sufficient to fabricate CIGS solar cells with conversion efficiencies up to 18.2 %. The JSC is in general 2 mA/cm2 higher, and the VOC 30 mV lower, for cells with the ZTO buffer layer as compared to cells with the traditional CdS buffer layer. In the end comparable efficiencies are obtained for the two different buffer layers. The gain in JSC for the ZTO buffer layer is associated with lower parasitic absorption in the UV-blue region of the solar spectrum and it is shown that the JSC can be increased further by making changes to the other layers in the traditional CdS/i-ZnO/ZnO:Al window layer structure. The ZTO is highly resistive, and it is found that the shunt preventing i-ZnO layer can be omitted, which further increases the JSC. Moreover, an additional increase in JSC is obtained by replacing the sputtered ZnO:Al front contact with In2O3 deposited by ALD. The large gain in JSC for the ZTO/In2O3 window layer stack compensates for the lower VOC related to the ZTO buffer layer, and it is demonstrated that the ZTO/In2O3 window layer structure yields 0.6 % (absolute) higher conversion efficiency than the CdS/i-ZnO/ZnO:Al window layer structure.

The design of an experimental ground layer adaptive optics (GLAO) system that uses a low altitude Rayleigh laser guide star as a wavefront reference source is presented. GLAO is a technique for achieving wide-field partial adaptive optics correction of the aberrations in a wavefront due to the effects of propagation through a turbulent atmosphere. The theoretical performance of the GLAO sub-systems, such as the laser launch system, wavefront sensor and optical train are analysed and compared, where possible, to measurements taken both under laboratory conditions and on-sky at the William Herschel Telescope.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, February, 2021
Vita. Cataloged from the official PDF of thesis.
Includes bibliographical references.
Over the past few decades, research in therapeutic cancer vaccines has achieved remarkable advances in both pre-clinical and clinical studies. However, strategies to boost antigen presentation and T cell priming in order to increase the fraction of patients responding to immunotherapy remains an urgent need. For the delivery platform, we applied microneedle (MN) skin patches to transdermally deliver vaccines to activate the potent epidermal Langerhans cells and dermal dendritic cells. The drug was incorporated as a releasable multilayer coating on the microneedle surface constructed with alternating absorption of oppositely charged species including protein or nucleic acid drugs and biocompatible polymer carriers, forming a 'sticky' layer-by-layer (LbL) film through electrostatic attraction. Past LbL MN strategies have all retained this 'sticky' nature and therefore require a long application time (15-90 mins) for drug implantation.
To resolve this problem, we devised a pH-induced charge-invertible polymer as a lift-off layer that significantly shortens the application time to 1 min. Our approach has inspired other work involving rapid film lift-off with charge-invertible species. On the drug side, we focused on the stimulator of interferon genes (STING) pathway. Current strategies mostly focus on developing synthetic vehicles to deliver the STING agonist, cyclic GMP-AMP (cGAMP) into the cells. However, this assumes the presence of fully functional STING protein to bind cGAMP. STING signaling has not only been shown to be frequently impaired in cancer cells due to epigenetic silencing of the protein; it is also under debate whether the overall population is responsive to delivery of just the agonist, since 19% of humans carry a mutated STING variant called HAQ STING that has been suggested to exhibit impaired function.
To address these challenges, we engineered a recombinant STING protein without the transmembrane domain (STING[delta]TM) that could be used as a functional carrier for cGAMP delivery and elicit type I IFN expression in cell lines deficient of STING or with defective endogenous STING. In vivo, our cGAMP-STING[delta]TM signaling complex elicited enhanced antigen specific B and T cell responses as well as robust anti-tumoral immunity in a B16 melanoma and a MC38 colon cancer mouse model.
by Yanpu He.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

Published Article
Until recently solid freeform fabrication (SFF) technology has been used mostly for production of prototype parts. However, as this technology matures, the initiative of utilising it for the manufacture of end-use products is establishing itself. As this tendency to use SFF for actual production runs increases, a demand is developing for sets of process-specific design for manufacture (DFM) guidelines that will assist designers who are designing parts for manufacture by a specific rapid manufacturing (RM) process. The purpose of this paper is to provideRMdesigners with such a series of processspecific design for manufacture guidelines.

While considerable progress has been made towards understanding the effect that membrane-based layer-by-layer (LbL) immobilizations have on the activity and stability of enzymatic catalysis, detailed work is required in order to fundamentally quantify and optimize the functionalization and operating conditions that define these properties. This work aims to probe deeper into the nature of transport mechanisms by use of pressure-induced, flow-driven enzymatic catalysis of LbL-functionalized hydrophilized poly(vinyldiene) (PVDF)-poly(acrylic acid) (PAA)-poly(allylamine hydrochloride) (PAH)-glucose oxidase (GOx) membranes. These membranes were coupled in a sealed series following cellulose acetate (CA) membranes for the elimination of product accumulation within the feed-side solution during operation. At pH = 6 and T = 21oC, the enzymatic catalysis of LbL-immobilized GOx from Aspergillus niger performed remarkably well in comparison to the homogeneous-phase catalysis within an analogous aqueous solution. On average, the enzymatic turnover was 0.0123 and 0.0076 mmol/(mg-GOx)(min) for the homogeneous-phase catalysis and the LbL-immobilized catalysis, respectively. Multiple consecutive permeations resulted in replicable observed kinetic results with R2 > 0.95. Permeations taking place over the course of a three week trial period resulted in a retention of >90% normalized activity when membranes were removed when not in use and stored at -20oC, whereas the homogenous-phase kinetics dropped below 90% normalized activity in under one day.

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.
Includes bibliographical references (leaf 53).
by Marina Zhurakhinskaya.
M.Eng.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Spray-assisted layer-by-layer (Spray-LbL) assembly is used to achieve vertical transfer of silicon microwire arrays into an ion-conducting, ultrathin polymer membrane. The choice of LbL platform and the properties of the silicon surface control the film morphology, generating either a conformal coating around each wire or a bridging film across the top of the array. Multilayer transfer printing is used to merge together separately assembled free-standing membrane/microwire assemblies into a single functional film. This technique offers an attractive option relative to traditional materials for microfabrication of Si devices such as solar-driven water splitting systems, capacitors, or electrochemically active electrodes. Transparent mixed conducting polymer films with conductivity above 0.1 mS/cm are highly desirable for photoelectrochemical cell membrane applications. Mixed conducting polymer composite PEDOT:sPPO was incorporated into LbL films and the composition ratio of the film components was varied to generate a series of films with tunable transparency and electrical and protonic conductivities. The visible light transmission properties are excellent: 1.1 [mu]m thick films with 150 mS/cm electrical conductivity have 80% transmission of light in the visual range. The electronic and ionic conductivities are inversely related, as one can be increased at the expense of the other. The highest ionic conductivity recorded was 4 mS/cm for 4.6 [mu]m thick films with 2 mS/cm electrical conductivity. Electron microscopy was used to provide insight into the effect of film morphology on electrical conductivity, and temperature dependent impededance spectroscopy and ion exchange capacity measurements yielded insight into the ionic conductivity changes.
by Nicole R. Davis.
Ph. D.

Organische Solarzellen bieten die Aussicht auf eine ökologische und zugleich ökonomische Energiequelle. Nachteile des Konzepts liegen in der z.T. geringen Stabilität der für Absorption und Ladungstransport verwendeten Moleküle und einer unvollständigen Ausnutzung des Sonnenspektrums. Zur Verbesserung beider Merkmale werden in dieser Arbeit einzelne organische Bestandteile durch anorganische Materialien mit hoher Stabilität und breiten Absorptionsbanden ersetzt. Insbesondere werden als Absorber kolloidale Quantenpunkte (QP) verwendet, denen aufgrund nicht-linearer und durch Größeneffekte steuerbarer optischer Eigenschaften in der Photovoltaik der dritten Generation großes Interesse gilt. Dazu werden dünne anorganisch-organische Filme mit einem Verfahren hergestellt, das auf Wechselwirkungen zwischen Partikeln in Lösung und geladenen Oberflächen beruht (electrostatic layer-by-layer self-assembly). TiO2-Nanokristalle als Elektronenleiter, kolloidale CdTe- und CdSe-QP als Absorber und konjugierte Polymere als Lochleiter werden in die Filme integriert und diese als aktive Schichten in photovoltaischen Zellen verwendet. Die Struktur der Filme wird zunächst mittels AFM, SEM, XPS sowie durch eine Beladung mit organischen Farbstoffen untersucht. Sie weisen Porosität auf einer Skala von Nanometern sowie eine kontrollierbare Dicke und Mikrostruktur auf. Darauf aufbauend werden durch weitere lösungsbasierte Prozessschritte photovoltaische Zellen gefertigt und Zusammenhänge zwischen Struktur und Zellenleistung elektronisch und spektroskopisch untersucht. Einflussfaktoren der Zelleffizienz wie die Ladungsträgererzeugung und interne Widerstände können so bestimmt und die Effizienz von CdSe-QP als Sensibilisatoren nachgewiesen werden. Die Arbeit demonstriert die Eignung der gewählten Methoden und Zelldesigns zur Herstellung von photovoltaischen Zellen und eröffnet neue Ansätze für die Entwicklung und Fertigung insbesondere auf QP basierender Zellen.
Organic solar cells offer the prospect of a both ecological and economical energy source. Drawbacks of the concept are low stabilities of the molecules used for absorption and charge transport and an incomplete utilization of the solar spectrum. In order to improve both these characteristics, individual organic components are replaced by inorganic materials with a high stability and broad absorption bands in this work. In particular, colloidal quantum dots (QDs) are used as absorbers, the non-linear and size controllable optical properties of which are attracting great interest in third generation photovoltaics. For this application, inorganic/organic thin films are produced with a method based on interactions between particles in solution and charged surfaces (electrostatic layer-by-layer self-assembly). TiO2-nanocrystals as electron conductors, colloidal CdTe- and CdSe-QDs as absorbers and conjugated polymers as hole conductors are integrated into the films, which are used as active layers in photovoltaic cells. The structure of the films is investigated by AFM, SEM, XPS and by loading the films with organic dye molecules. The films show porosity on a nanometer scale as well as a controllable thickness and microstructure. Complemented by further solution based processing steps, photovoltaic cells are manufactured and correlations between the structure and performance of the cells are investigated both electronically and spectroscopically. Individual factors that determine the cell efficiency, such as carrier generation and internal resistances, are determined and the efficiency of CdSe-QDs as sensitizers is demonstrated. This work proves the suitability of the chosen methods and cell designs for manufacturing photovoltaic cells and opens up new approaches for the development and manufacture of in particular QD-based solar cells.

Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2008.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 41-45).
Although perfectly matched layers (PMLs) have been widely used to truncate numerical simulations of electromagnetism and other wave equations, we point out important cases in which a PML fails to be reflectionless even in the limit of infinite resolution. In particular, the underlying coordinate-stretching idea behind PML breaks down in photonic crystals and in other structures where the material is not an analytic function in the direction perpendicular to the boundary, leading to substantial reflections. The alternative is an adiabatic absorber, in which reflections are made negligible by gradually increasing the material absorption at the boundaries, similar to a common strategy to combat discretization reflections in PMLs. We demonstrate the fundamental connection between such reflections and the smoothness of the absorption profile via coupled-mode theory, and show how to obtain higher-order and even exponential vanishing of the reflection with absorber thickness.
by Ardavan F. Oskooi.
S.M.

In-situ geotechnical testing of surficial sediment layers in areas of active sediment dynamics can provide essential information about physical and geotechnical variations of sediment properties with regards to active sediment remobilization processes. For example, portable free fall penetrometers (PFFPs) can assist with the detection of mobile sediment layers. They are easy to deploy, and can provide a large spatial coverage in a time- and cost-effective manner. However, they often struggle to provide more detailed information about the properties of mobile sediment layers due to a lack of calibration and validation in existing data sets. Currently, existing sediment samplers often disturb, or ignore the uppermost sediment layers. Simultaneous sediment sampling and geotechnical profiling is needed to fill this gap, and to drive data interpretation forward. A field investigation of surficial sediments was conducted in the wetland waterways of coastal Louisiana in 2014. In-situ tests were conducted using PFFP, and disturbed sediment samples were collected in selected locations. The results allowed us to map changes in sediment strength and stratification, and correlate the geotechnical results to local site characteristics. However, the need for high quality sediment samples for calibration and validation was emphasized by the results. Three different sediment sampler add-on units targeting mobile layers were designed and manufactured based on lessons-learned from the literature. The designs were tested in the laboratory and in the field (Yakutat, Alaska and York River, Virginia) in 2017. The samples were analyzed to understand the influence of different sampler characteristics on collected sample quality, and, to define mobile layer sampler characteristics that enable simultaneous geotechnical testing and the collection of high quality samples. Following field survey campaigns in the York River, Virginia in 2016 allowed to assess surficial sediment layer characteristics and behavior based on a coupled analysis of geotechnical data from in-situ PFFP tests and the sedimentological data collected using box cores and the novel sediment sampler. In summary, novel strategies and instrumentation to carry out simultaneous sediment sampling and geotechnical profiling of seabed surface layers were tested, and new pathways for geotechnical data analysis for the investigation of mobile seabed layers were presented.
PHD

The Prosthetic Device Communication Protocol is a CAN-based protocol developed specifically for use within prosthetic devices, for connecting the components of the device, most importantly sensors and actuators. The lower levels of this protocol have already been developed. This thesis focuses on developing a device profile layer, to bring plug-and-play functionality to the protocol.Specifically, this thesis contains a proposed device profile layer, a description of an implementation of the profile layer, and testing of this implementation. Testing results were largely successful, most of the desired functionality was achieved in the implementation.

There is a great activity in the research community towards the investigations of the various aspects of 5G at different protocol layers and parts of the network. Among all, physical layer design plays a very important role to satisfy high demands in terms of data rates, latency, reliability and number of connected devices for 5G deployment. This thesis addresses he latest developments in the physical layer algorithms regarding the channel coding, signal detection, frame synchronization and multiple access technique in the light of 5G use cases. These developments are governed by the requirements of the different use case scenarios that are envisioned to be the driving force in 5G. All chapters from chapter 2 to 5 are developed around the need of physical layer algorithms dedicated to 5G use cases. In brief, this thesis focuses on design, analysis, simulation and he advancement of physical layer aspects such as 1. Reliability based decoding of short length Linear Block Codes (LBCs) with very good properties in terms of minimum hamming istance for very small latency requiring applications. In this context, we enlarge the grid of possible candidates by considering, in particular, short length LBCs (especially extended CH codes) with soft-decision decoding; 2. Efficient synchronization of preamble/postamble in a short bursty frame using modified Massey correlator; 3. Detection of Primary User activity using semiblind spectrum sensing algorithms and analysis of such algorithms under practical imperfections; 4. Design of optimal spreading matrix for a Low Density Spreading (LDS) technique in the context of non-orthogonal multiple access. In such spreading matrix, small number of elements in a spreading sequences are non zero allowing each user to spread its data over small number of chips (tones), thus simplifying the decoding procedure using Message Passing Algorithm (MPA).

An advanced laser-Doppler velocimeter is designed to acquire fully-resolved turbulence structural measurements in high Reynolds number two- and three-dimensional turbulent boundary layers. The new instrument combines, for the first time, new techniques allowing for the direct measurement of particle acceleration and sub-measurement-volume-scale position resolution so that second-order 3D particle trajectories may be measured at high repetitions. Using these measurements, several terms in the Reynolds stress transport equations may be directly estimated, giving new data for modeling and understanding the processes leading to the transport of turbulence in boundary layer flows. Due to the unique performance of the probe, many aspects of LDV instrumentation development were addressed. The LDV configuration was optimized for lowest uncertainties by considering the demanding applications of particle position and acceleration measurements. Low noise light detection and signal conditioning was specified for the three electronic channels. A high-throughput data acquisition system allows for exceptional burst rate acquisition. Signal detection and processing algorithms have been implemented which draw from previous techniques but also address distinctive problems with the current system. In short, the instrument was designed to advance the state-of-the-art in LDV systems. Measurements presented include turbulence dissipation rate and fluctuating velocity-pressure gradient correlations that have been measured in 2D and 3D turbulent boundary layers using the unique capabilities of the CompLDV--many of these measurements are the first of their kind ever acquired in high Reynolds number turbulent flows. The flat-plate turbulent boundary layer is studied at several momentum thickness Reynolds numbers up to 7500 to examine Reynolds numbers effects on terms such as the velocity-pressure gradient correlation and the dissipation rate in the Reynolds transport equations. Measurements are also presented in a pressure-driven three-dimensional turbulent boundary layer created upstream from a wing-body junction. The current results complement the extensive data from previous studies and provide even richer depth of knowledge on the most-completely-documented 3D boundary layer flow in existence. Further measurements include the wakes of three circular-cylinder protuberances submerged in a constant pressure turbulent boundary layer.
Ph. D.

Surface chemistry of wood is based on the exposed cut surface that is the combination of intact (lumen wall) and cut cell wall material. It is inherently complex and changes with history of processing. Modification of wood surface through noncovalent attachment of amine containing water soluble polyelectrolytes provides a path to create functional surfaces in a controlled manner. Furthermore, modification of the surface can be performed using layer-by-layer (LbL) assembly, where the adsorption of polyelectrolytes or nanoparticles in sequential steps yields a multilayer film with a defined layer sequence on a given substrate. The objective of this study was to quantify adsorption of polyelectrolytes onto wood surface and use these polyelectrolytes as adhesives. In this study, optimal pH conditions for modifying wood surfaces, by anchoring adsorbing polyelectrolytes, were detected using zeta- ( )-potential measurements. Positively charged wood surfaces were also detected by the same technique after a layer of poly(diallyldimethylammonium chloride) (PDDA) or poly (ethylenimine) (PEI) was adsorbed. Both X-ray photoelectron spectroscopy (XPS) and Carbon-Nitrogen-Sulfur analyzer (CNS) were used to quantify the amount of charged polymer on wood surfaces to elucidate optimal pH and ionic strength for polyelectrolyte adsorption. Confocal laser scanning microscopy (CLSM) and Environmental Scanning Electron Microscope (ESEM) were used to characterize adsorbed LbL multilayers of poly(acrylic) acid (PAA) and poly(allylamine hydrochloride) (PAH). Cross-linking between PAA and PAH at various temperatures was studied by Fourier Transform Infrared Spectroscopy (FTIR) and the evaluation of multilayer as bonding agents was carried out by compression shear test following ASTM D905 standard.
Master of Science

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 82-83).
The operational parameters of the automated Spray-LbL technique for thin film deposition have been investigated in order to-identify their effects on film thickness and roughness. We use the automated Spray-LbL system developed at MIT by the Hammond lab to build 25 bilayer films of poly (ally amine hydrochloride) (PAH) and poly (acrylic acid) (PAA). Each of the 10 operational parameters of this system are explored individually to isolate each parameter's effect on film thickness and roughness. The parameter effects are analyzed for apparent trends to determine the parameters best suited for adjusting film thickness and roughness. The optimal parameters for thickness adjustment are polyelectrolyte solution concentration, polyelectrolyte spray time, spraying distance, air pressure and polyelectrolyte charge density. These parameters are independent of the type of species used to construct the film, and thus the trends should apply to any species used to construct thin films. The effect of each of the 10 operational parameters is examined in detail. While researching the parameter effects, polyelectrolyte interdiffusion in the films was observed. This interdiffusion is investigated using both the conventional dipped LbL and Spray-LbL deposition techniques. Interdiffusion is shown to be dependent on 3 factors, the charge density of the polyelectrolytes, the molecular weight of the polyelectrolytes, and the contact time between the polyelectrolyte solutions and the surface of the film. Interdiffusion is observed when the PAH is partially charged, the polyelectrolytes chains have a low molecular weight, and the contact time is sufficiently long enough to allow for interdiffusion. The significantly reduced contact time during the automated Spray-LbL process not only speeds up the film deposition time, but also significantly hinders the interdiffusion of PAH resulting in much thinner films than what is possible from dipping. Finally, the uniformity of the films produced using the automated Spray-LbL system is investigated. Films deposited on substrates greater than 1 in diameter area exhibit more than 20% variance in thickness. Adjustments were made to the setup of the system in an effort to expand this area of film thickness uniformity. However, it is determined that the design of this automated Spray-LbL system limits the film uniformity to an area of 1 in diameter.
by James Hart Gifford.
S.M.

Layer-by-layer deposition techniques were used to fabricate films with second order nonlinear optical (NLO) properties. These materials are key to the development of electro-optic modulators used in fiber optic communication systems. Performance benefits and lower manufacturing costs are driving the development of organic NLO materials as replacements for inorganic crystalline materials such as lithium niobate. The layer-by-layer deposition technique in which polyelectrolytes are deposited on a surface by electrostatic effects is called the Ionically Self-Assembled Monolayer or ISAM method. The role of the optically inactive polycation's structure on deposition and chromophore orientation was studied by fabricating films with several different polycations. While the specific interactions responsible for chromophore orientation in ISAM films remains unclear, hydrogen bonding and electrostatic effects are ruled out as the sole sources of orientation. The highest values of &967;(2) were observed under pH conditions that resulted in flat and thin layers. The relationship between pH and the optical homogeneity of the film was also explored. Deposition of polymers under pH conditions in which the polymer chains were aggregated in solution results in films that are not suitable for use in devices. In this work, a new layer-by-layer deposition technique was developed. Coined hybrid deposition, it relies on covalent bonds and electrostatic interactions for film fabrication. Optically inactive polyamines were used as sources of positive charges and as binding sites with optically active low molecular weight chromophores functionalized with a reactive triazine ring and negative charged sulfonate groups. Polar ordering of the chromophores was obtained when the deposition was done under conditions in which covalent bonding was the preferred attachment mechanism for the chromophore molecules. pH conditions in which electrostatic attachment dominated resulted in poorer orientation. The effect of adding ionic salts to the dye solutions was studied, with hopes of increasing the chromophore density in the film by shielding inter-dye electrostatic repulsions. A linear relationship in deposited amount, as characterized by absorbance/bilayer, was observed as the salt concentration was increased. Little effect on &967;(2) was observed for films made with the as-received Procion Red MX-5B chromophore. However, films fabricated from purified Procion Brown MX-GRN showed a definite dependence on added salt. Exceptional &967;(2) values were obtained for Procion Brown films deposited using 0.5 M NaCl and PAH. The importance of depositing from non-aggregated solutions was again highlighted, as films made with the less soluble Procion Orange were significantly less homogeneous than those made from Procion Red and Procion Brown which were highly soluble. The role of polycation structure on the deposition and orientation of Procion Brown and Red was examined.
Ph. D.

Tissue engineered constructs often fail due to poor integration with the patient’s tissues. Specifically, they fail to be vascularised, leading to the death and loss of the implanted tissues. Thus, there is a need to produce angiogenic materials to improve tissue integration. We describe the development of a layer-by-layer (LBL) approach to coat electrospun scaffolds to help promote angiogenesis into these biomaterials once implanted. Initially, Electrospun poly-L-lactic acid (PLLA) was coated comparing two different techniques – one using alternative layers of PolyEthyleneImine (PEI) and PolyAcrylic Acid (PAC) and one with alternative layers of PEI and heparin (HEP) for a total of seven layers in both cases. Both scaffolds were then coated with heparin as the final layer. The scaffold coated with alternate PEI and PAC showed a clear ability to bind the most heparin. This scaffold was then studied further for its ability to bind VEGF which was confirmed using an ELISA. The scaffold coated with 7 alternate layers of PEI and PAC and heparin was then implanted in a chick chorionic allantoic membrane (CAM) assay. After a period of 7 days in the CAM, the coated scaffold showed strong angiogenic activity. In contrast, the uncoated scaffolds did not promote angiogenesis. Sub sequentially, this approach was used to coat two other different materials, electrospun polyurethane and a commercially available polypropylene mesh. They were also implanted into the chick CAM. We conclude that this approach to functionalising scaffolds is effective within a clinically relevant time period (7 days in an in vivo angiogenic model) and suggest this will be useful for improving integration of scaffolds once implanted.

Ce travail est consacré à la synthèse de nouveaux polymères donneurs de liaison Hydrogène et à leur utilisation comme partenaire dans la construction de nouveaux films multicouches préparés par le procédé d’élaboration en couche-par-couche (LbL). Plus particulièrement, une nouvelle réaction impliquant des mercaptoalcools non protégés et le poly(2,3,4,5,6-pentafluorostyrène) (PPFS) a été développé et appliquée à la synthèse de nouveaux polymères donneurs de liaisons H. Ce couplage régiosélectif et chimiosélectif de type « click » avec un thiol hétérofonctionnel peut être utilisée pour préparer une bibliothèque de polymères qui diffèrent de par leur degré de substitution (DS) et/ou leur fonctionnalité en groupements associatifs. Le contrôle de ces paramètres structuraux permet de moduler leur force d’interactions avec des partenaires accepteurs de liaison H variés, comme la poly(4-vinyl pyridine) (P4VP), le poly(acrylate de n-butyle) (PBA) et le poly(oxyde d'éthylène) (PEO), de telle façon que tous les types de mélanges binaires (mélange non miscible, partiellement ou totalement miscible, ou complexe interpolymère) peuvent être obtenus. Ensuite, les dérivés de PPFS donneurs de liaisons H ont été utilisés en partenariat avec le P4VP pour élaborer avec succès de nouveaux films multicouche dont la force motrice est l’établissement de liaisons H. L'influence de nombreux paramètres relatifs à la structure des polymères donneurs (DS, structure chimique du groupement associatif), au type de modification chimique subie par le substrat sur lequel est élaboré le film multicouche (monocouche auto-assemblée vs. polymère greffée en conformation de type brosse) ou encore des paramètres expérimentaux liés aux conditions de dépôt (concentration des solutions de dépôt, nature du partenaire adsorbé en premier) a été étudiée. Plus particulièrement, le mécanisme de croissance ainsi que les caractéristiques de surface du film ont été évalués
This work deals with the design of novel hydrogen-bond donor polymers and their use as partner in new tailor-made multilayered films prepared by the layer-by-layer (LbL) process. In this context, a novel regioselective and chemoselective “click-type” reaction of unprotected mercaptoalcohols onto poly(2,3,4,5,6-pentafluoro-styrene) (PPFS) has been developed, and applied to the synthesis of new hydroxylated H-bond donor polymers. This coupling with heterofunctional thiol is used to prepare a library of polymers differing in the degree of substitution (DS) and/or functionality. The fine control of these parameters makes it possible to tune their interaction ability with various acceptor polymers such as poly(4-vinyl pyridine) (P4VP), poly(n-butyl acrylate) (PBA) and poly(ethylene oxide) (PEO), such that all possible scenarios (immiscible blend, partially or totally miscible blend or interpolymer complex) can be achieved. Subsequently, the resulting H-bond donor polymers (PPFS derivatives) were used to successfully build-up multilayered films with using P4VP as partner via layer-by-layer (LbL) through the dip deposition process. The influence of various parameters related to structure of the partners (DS, nature of the PPFS derivatives), the chemical structure of the surface onto which the film is built-up (self-assembled monolayer vs. polymer brush) and the deposition process (concentration of deposition solutions, nature of the first deposited partner) was in-depth evaluated, on both the growth mechanism and on the surface features of the multilayered films

Thesis (S.M. in Mechanical Engineering and S.M. in Ocean Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (p. 159-164).
Air-water interaction flow between two parallel flat plates, known as Couette flow, is simulated by direct numerical simulation. The two flowing fluids are coupled through continuity of velocity and shear stress condition across the interface. Pseudo-spectral method is used in each flow subdomain with Fourier expansion in streamwise and spanwise directions and finite difference in vertical direction. Statistically quasi-steady flow properties, such as mean velocity profiles, turbulent intensities, Reynolds stress and turbulent kinetic energy (TKE) budget terms show significant differences between air-water interface turbulence near the water side (IntT-w) and wall-bounded turbulence(WT) while there are some similarities between IntT-w and free surface turbulence (FST). Due to the velocity fluctuation at the interface, water side near interface turbulence flow (IntT-w) is characterized with a thinner viscous sub-layer and decreased intercept parameter B in log-law layer, strengthened Reynolds stress and eddy viscosity, together with a stronger production term, decreasing-then-increasing dissipation term and negative turbulent diffusion term in TKE budget.
(cont.) Abundant physical phenomena exist on the water side turbulent flow with four major types of three-dimensional vortex structures identified near the interface by variable-interval spacing averaging (VISA) techniques. Each type of vortex structures is found to play an essential role in the turbulent energy balance and passive scalar transport.
by Song Liu.
S.M.in Mechanical Engineering and S.M.in Ocean Engineering

We propose a development of carbon nanotube (CNT)/albumin nanocomposite for 2D and 3D tissue organization by cell growth. The adhesion and proliferation for neuroblastoma and fibroblast cells have been investigated on films based on CNT/bovine serum albumin (BSA) nanocomposite. Single-walled car-bon nanotube (SWNT)/BSA composites can be used as a substrate for cell growth of different kind. The layers of nanocomposite properties growing method based on laser radiation action. Investigations of sta-bility, an adhesion and internal structure of layers were performed. Stabilizing properties of the described laser method of manufacture (laser nanoforming) of layers may be associated with the ability to obtain nanotube frame work in composite structure under action of electric field of directed laser radiation. The presence of a such frame creates the conditions for self-assembly of biomedical tissues. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35452

The transmission of haptic information over the network has recently received significant attention. The wide spectrum of haptic applications makes it difficult to capture the widely varying requirements of these applications into one generic protocol. In this paper, we introduce ALPHAN (Application Layer Protocol for Haptic Networking), a novel application layer protocol for haptic communication. The protocol is strategically placed at the application layer so that it can easily be customized according to the application requirements and needs. An extension to the HAptic Meta-Language (HAUL) is proposed to define its networking parameters. The protocol introduces the concept of Multiple Buffering where priorities are attributed to different sending buffers in a collaborative haptic environment. The protocol also supports some concepts introduced in previous haptic communication protocols like local lag and key packets.

Satellite resource management efficiency has been identified as one of the key factors in the commercial success of mobile satellite systems, since optimisation of all link budget elements is crucially important in order to make the most out of the satellite limited resources (bandwidth, power) which in turn have a direct impact on the cost of the system. The compensation techniques used in order to overcome the fading effects experienced in the link are generally applied by considering the worst-case channel conditions, resulting in inefficient utilisation of the transmission power as well as frequency spectrum. There is no dynamic control adaption used in current mobile satellite systems except simple power control. In addition, a single scheme is neither capable of providing an optimum solution for fade mitigation nor closing the link budget at all times. Therefore, it is necessary to use more than one technique at a time which offers the best solution in terms of spectrum and power efficiency. The efficiency of conventional systems, therefore, can be improved if it has the ability to match the effective user bit rate to the channel conditions by using a hybrid scheme. Hence, the aim of our work is to develop a physical layer by using a hybrid scheme, which results in higher throughput under favourable channel conditions. This technique also introduces a reduction of the data rate during bad channel conditions without the need to increase the transmitted power significantly. The novelty of this research work is centred on the switching mechanism used for such adaptations. For the first time, we propose an adaptive system based on the Rice factor variation. The suitability of this parameter for the proposed adaptive system is investigated first by considering the real time variation in the environment. We are proposing a feed back type of system in which the receiver estimates the Rice factor and sends it to the transmitter. Upon receiving this information, the transmitter selects the optimum modulation and coding scheme for the transmission in order to improve spectral and power efficiency of the system. In order to develop an adaptive physical layer, the main issues related to mobile satellite systems should be identified. Therefore, the key differences between the terrestrial and satellite mobile communication systems are presented at the beginning. A brief description about T/S-UMTS and the air interfaces proposed for standardisation of S-UMTS are presented and compared in the following chapter. Subsequently, a suitable baseline model was chosen and the simulation aspects are presented. The following chapter presents some of the parameters that have to be estimated in order to develop an adaptive physical layer. The performance evaluation of adaptive modulation and coding is presented in the last chapter. Key words: S-UMTS, SW-CDMA, Adaptive modulation and coding. Rate matching, SNR estimation, modulation detection. Rice factor estimation. Histogram comparison. Re-encoding.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.
Includes bibliographical references (p. 98-103).
Overlay networks are virtual networks formed by cooperating nodes that share an underlying physical network. They represent a flexible and deployable approach for applications to obtain new network semantics without modification of the underlying network, but they suffer from efficiency concerns. This thesis presents two new primitives for implementation in the network layer (i.e., the routers of the physical network). These primitives support the efficient operation and construction of overlay networks. Packet Reflection allows end hosts to request that routers perform specialized routing and duplication for certain packets. Path Painting allows multiple end hosts to determine where their disparate paths to a rendezvous point meet, in order to facilitate overlay topology building that reflects the topology of the underlying network. Both primitives can be incrementally deployed for incremental benefit. This thesis describes a variety applications of these primitives: application level multicast systems with various semantics, an extended Internet Indirect Infrastructure with latency benefits over the original proposal, and an extension to Chord which would allows faster lookups. Experimental results on simulated topologies indicate that when all routers support the proposed primitives, less that 5% overhead (in terms of link usage and latency) remains in two common overlay network usage scenarios. In addition, the benefits gained from deployment are significant even at low deployment levels. At approximately 25% deployment, the primitives have reduced overhead by over 50%. When intelligent deployment strategies are used, link usage overhead is less than 30% at less than 10% deployment. Finally, the results indicate that these benefits affect the area local to the deployed routers, providing a deployment incentive to independent networks.
by John Jannotti.
Ph.D.

This thesis presents the novel application of microwave technology to the process of additive layer manufacturing (ALM). A particle size sensor, based on microwave cavity perturbation, is described and subsequently demonstrated by the measurement of the complex permeability of a series of Titanium powders. The results are compared with existing theory and finite element simulations of metallic powders. The ability to discern changing particle size distributions is important in ensuring the reliable operation of selective laser melting machines but, to remain industrially relevant, it is vital that the proposed system can be produced at low cost. By way of demonstration, the design and construction of an inexpensive scalar network analyser was completed. A systematic study of surface resistance of a number of metal surfaces, produced by Selective Laser Melting, was undertaken. Using a dielectric resonator with a “lift-off” calibration procedure, the losses of surfaces manufactured in orthogonal orientations and different surface finishes were compared. Surface roughness measurements showed that microwave losses were not monotonically dependent on root-mean-square surface roughness; this was attributed to differing roughness feature size distributions. For microwave characterization of materials over a wide temperature range, it is often desirable to perform cavity perturbation measurements at elevated temperatures. However, it is shown here that heat treatment can permanently modify the surface resistance of a metal surface and potentially lead to inaccurate perturbation results. X-Ray diffraction measurements confirm the source of modification is due to changes in surface stress and the appearance of solution precipitates. The sensitivity of microwave measurements to surface stress also demonstrates the potential for microwave assessment of surfaces produced by ALM. Finally, to stimulate further work in this area, the design of a single mode microwave heating system was discussed and a prototype developed.

Le dépôt de couche atomique (ALD) est devenu une technique essentielle de dépôt en phase vapeur de couches minces pour de nombreuses applications. La demande croissante de composants électroniques et de matériaux nanostructurés a fait de gls{ald} l'un des processus de fabrication clés du marché des nanotechnologies.Dans ce travail, nous présentons de nouveaux matériaux nanostructurés pouvant être utilisés comme transducteurs dans des dispositifs à biocapteurs. Ces matériaux ont été préparés en combinant gls{ald} avec des techniques "top-down" et "bottom-up" telles que la lithographie par nanosphère (gls{nsl}), le dépôt physique en phase vapeur (gls{pvd}), la gravure chimie assistée par des métaux (gls{mace}) et électrodéposition.En tant que premier candidat prometteur, des nanofils de silicium (gls{sinws}) recouverts de ZnO par gls{ald} ont été fabriqués. Ces structures 3D sont très attractives pour les applications de biocapteurs optiques en raison de leur activité intense de photoluminescence (gls{pl}) à température ambiante. Dans une première approche, ces nanostructures coe ur/coquille ont été entièrement caractérisées et testées en tant que capteurs possibles pour la détection du peroxyde d’hydrogène, qui est un produit de réaction courant de plusieurs oxydoréductases.De plus, des nanostructures creuses en ZnO semblables à des oursins recouvertes de Au ont été préparées avec une taille contrôlée en combinant NSL, gls{ald}, électrodéposition et évaporation par faisceau d'électrons (gls{ebeam}). L’influence de l’épaisseur du film Au sur les capacités de diffusion Raman (gls{sers}) améliorées en surface des substrats a été étudiée. Les structures optimisées ont été utilisées pour détecter des molécules de thiophénol avec une limite de détection (gls{lod}) de SI{e-8}{Molar}. De plus, l'adénine peut être détectée avec une concentration aussi basse que SI{e-6}{Molar}. L'excellente uniformité et la répétabilité lot par lot des substrats en font d'excellents candidats pour une détection et une biocapture SERS fiables.En outre, un groupe diversifié de nouveaux matériaux présentant des caractéristiques attrayantes qui peuvent être facilement appliqués à la détection, à la catalyse et à la plasmonique est présenté. Des nanoparticules bimétalliques de Pd/Au supportées sur gls{sinws} avec gls{ald} et un remplacement galvanique ont été fabriquées. De plus, des structures ZnO creuses de type urchin avec ZIF-8 par électrodéposition ont été fabriquées pour de possibles applications SERS
Atomic layer deposition (gls{ald}) has emerged as an essential vapor deposition technique of thin films for countless applications. The rising demand for electronic components and nanostructured materials has established gls{ald} as one of the key fabrication processes in the nanotechnology market.In this work, novel nanostructured materials that can be used as transducers in biosensor devices are presented. These materials have been prepared by a combination of gls{ald} with top-down and bottom-up techniques such as nanosphere lithography (gls{nsl}), physical vapor deposition (gls{pvd}), metal-assisted chemical etching (gls{mace}), and electrodeposition.As a first promising candidate, silicon nanowires (gls{sinws}) covered with ZnO by gls{ald} were fabricated. These 3D structures are quite attractive for optical biosensing applications thanks to their intense photoluminescence (gls{pl}) activity at room temperature. As a first approach, these core/shell nanostructures were fully characterized and tested as possible sensors for the detection of hydrogen peroxide, which is a common reaction product of several oxidoreductases.In addition, Au-covered hollow urchin-like ZnO nanostructures were prepared with controlled size by combining NSL, gls{ald}, electrodeposition, and electron beam (gls{ebeam}) evaporation. The influence of the Au film thickness on the surface-enhanced Raman scattering (gls{sers}) capabilities of the substrates was investigated. The optimized structures were used to detect thiophenol molecules with a limit of detection (gls{lod}) of SI{e-8}{Molar}. Additionally, adenine can be detected with a concentration as low as SI{e-6}{Molar}. The excellent uniformity and batch-to-batch repeatability of the substrates makes them excellent candidates for reliable SERS sensing and biosensing.Moreover, a miscellaneous group of novel materials with enticing features that can be readily applied in sensing, catalysis, and plasmonics is presented. Bimetallic Pd/Au nanoparticles supported on gls{sinws} with gls{ald} and galvanic replacement were fabricated. Furthermore, hollow urchin-like ZnO structures with ZIF-8 via electrodeposition were fabricated for possible SERS applications

This thesis concerns the Multi-layer Perceptron (MLP) model, one of a variety of neural network models that have come into wide prominence since the mid 1980s for the classification of individuals into pre-defined classes based on a vector of individual measurements. Each discipline in which the MLP model has had influence, including computing, electrical engineering and psychology, has recast the model into its own language and imbued it with its own concerns. This divergence of terminologies has made the literature somewhat impenetrable but has also led to an appreciation of other disciplines' priorities and interests. The major aim of the thesis has been to bring the MLP model within the frame­work of statistics. We have two aims here: one is to make the MLP model more intelligible to statisticians; and the other is to bring the insights of statistics to the MLP model. A statistical modeling approach can make valuable contributions, ranging from small but important clarifications, such as clearing up the confusion in the MLP literature between the model and the methodology for fitting the model, to much larger insights such as determining the robustness of the model in the event of outlying or atypical data. We provide a treatment of the relationship of the MLP classifier to more familiar statistical models and of the various fitting and model selection methodologies currently used for MLP models. A description of the influence curves of the MLP is provided, leading to both an understanding of how the MLP model relates to logistic regression (and to robust versions of logistic regression) and to a proposal for a robust MLP model. Practical problems associated with the fitting of MLP models, from the effects of scaling of the input data to the effects of various penalty terms, are also considered. The MLP model has a variable architecture with the major source of variation being the number of hidden layer processing units. A direct method is given for determining this in multi-class problems where the pairwise decision boundary is linear in the feature space. Finally, in applications such as remote sensing each vector of measurements or pixel contains contextual information about the neighboring pixels. The MLP model is modified to incorporate this contextual information into the classification procedure.

碩士
國立臺灣大學
大氣科學研究所
103
This study investigates the influences of boundary layer (BL) processes and the environmental conditions on the maintenance of advection fog through idealized large-eddy simulations. The initial conditions were simplified from the in-situ sounding data during the fog episode at Kinmen Island. A near saturated moist layer with temperature inversion is throughout the domain, which represents the characteristics of advection fog. This kind of vertical profile of moisture can influence the effects of turbulent mixing and longwave radiative cooling at fog top. A series of idealized large-eddy simulations were carried out using the Vector Vorticity equation cloud-resolving model at a high resolution of 4 m. By turning on/off selected physical processes, the results show that surface heat and moisture fluxes have little influence on liquid water content and are restricted to surface layer when the fog layer already exists. Longwave radiative cooling is the dominant process to generate fog water but in this case cannot effectively generate turbulent kinetic energy (TKE) through buoyancy flux due to the specific environmental moisture condition. Solar radiation heats and evaporates the liquid water content within the fog layer. Vertical wind shear enhances the turbulent mixing and extents the vertical distribution of fog layer. Vertical wind shear also drives the shear instability, and the averaged magnitude of shear production of TKE is much larger than that of buoyancy production of TKE in this case. As to evaluate the impact of environmental wind profiles on the maintenance of the fog layer, Richardson number (Ri) is identified as the critical parameter. The stronger vertical wind shear (Ri < 0.25) modifies the boundary layer from a stable boundary layer to a well-mixed boundary layer. As a result, the fog layer no longer maintains but shifts upward into stratus cloud. In contrast, the fog layer can maintain under the condition of weaker vertical wind shear (Ri > 0.25). Lastly, the sensitivity of the fog layer structure to both the environmental vertical wind shear and sea surface temperature (SST) is investigated. Results show that the combination of weaker vertical wind shear (Ri > 0.25) and colder SST is favorable to the maintenance of fog. However, warmer SST dissipates the fog layer in the condition of weaker vertical wind shear (Ri > 0.25). On the other hand, fog layer cannot exist in the condition of stronger vertical wind shear (Ri < 0.25) whether the SST is colder or warmer. This study suggests that the vertical profile of wind speed and the effect of turbulent transport have the most significant influence on the structure of advection fog. Therefore, when simulating the advection fog by regional models, the results would highly depend on whether the chosen BL and turbulence parameterization schemes and vertical resolution can accurately represent the transition between a stable and well-mixed BL.

Cloud computing has emerged in the last decade as a popular distributed computing service offered by commercial providers. Public Clouds offer pay-as-you-go access to elastic resources that can be acquired and released on-demand. Among IaaS providers, on demand Virtual Machines(VMs) give access to compute resources, and are one of the frequently used services. While these fi xed-price VMs have absolute reliability and availability, spot-priced VM offer much higher discount while being preemptible, trading-off reliability. For users running large workloads with many tasks on the Cloud, such deep discounts will be valuable, and should motivate them to incorporate spot VMs. However, when users want the benefi ts of both reliability and cost reduction, they require scheduling strategies for managing their workloads when running on spot VMs. More broadly, when we consider resources beyond the Cloud and in the Fog and Edge layers of the network, such unreliability and transience become common due to commodity hardware, network variability and device mobility. Scheduling single tasks, bags of tasks or data flows on such dynamic Edge, Fog and Cloud resources with diverse capacities is challenging. We propose techniques for reliable and efficient application scheduling on these resources. First, we propose an automated scheduling engine to manage decisions related to Cloud VMs. Specifically, AutoBoT manages spot and fixedprice VM acquisition, bid price, and release, and task placement, checkpointing and migration for a Bag of Tasks(BoT), within a guaranteed completion time specifi ed by the user while minimizing the cost paid by them to the Cloud provider. The use of spot-priced VMs enhances the pro t relative to running exclusively on reliable VMs. We also propose various checkpointing strategies. The experimental results show that our scheduler gives 80% pro t and rare but bounded losses, compared to using only fixed-price VMs. Further, its 100% completion guarantee is 23 􀀀 42% better than using only spot-priced VMs which offer a similar pro t. Second, the heuristics proposed for AutoBoT are extended to transient Edge and Fog resources. We propose heuristics for distributed scheduling of tasks of DAGs on mobile Edge resources, Fog devices and Cloud VMs such that the overall DAG's deadline is met and total monetary cost of the resources billed is minimized.