Consider a cognitive overlaid network (CON) that has two tiers with different priorities: a primary tier vs. a secondary tier, which is an emerging network scenario with the advancement of cognitive radio (CR) technologies. The primary tier consists of randomly distributed primary radios (PRs) of density n, which have an absolute priority to access the spectrum. The secondary tier consists of randomly distributed CRs of density m = n^y with y greater than or equal to 1, which can only access the spectrum opportunistically to limit the interference to PRs. In this dissertation, the fundamental limits of such a network are investigated in terms of the asymptotic throughput and packet delay performance when m and n approaches infinity. The following two types of CONs are considered: 1) selfish CONs, in which neither the primary tier nor the secondary tier is willing to route the packets for the other, and 2) supportive CONs, in which the secondary tier is willing to route the packets for the primary tier while the primary tier does not. It is shown that in selfish CONs, both tiers can achieve the same throughput and delay scaling laws as a stand-alone network. In supportive CONs, the throughput and delay scaling laws of the primary tier could be significantly improved with the aid of the secondary tier, while the secondary tier can still achieve the same throughput and delay scaling laws as a stand-alone network. Finally, the throughput and packet delay of a CON with a small number of nodes are investigated. Specifically, we investigate the power and rate control schemes for multiple CR links in the same neighborhood, which operate over multiple channels (frequency bands) in the presence of PRs with a delay constraint imposed on data transmission. By further considering practical limitations in spectrum sensing, an efficient algorithm is proposed to maximize the average sum-rate of the CR links over a finite time horizon under the constraints on the CR-to-PR interference and the average transmit power for each CR link. In the proposed algorithm, the PR occupancy of each channel is modeled as a discrete-time Markov chain (DTMC). Based on such a model, a novel power and rate control strategy based on dynamic programming (DP) is derived, which is a function of the spectrum sensing output, the instantaneous channel gains for the CR links, and the remaining power budget for the CR transmitter. Simulation results show that the proposed algorithm leads to a significant performance improvement over heuristic algorithms.

Atmospheric pressure microplasmas are uniquely characterized by their very high energy densities and also by their small discharge sizes. These properties allow for unique applications in plasma processing technologies. We have investigated the operational characteristics of microplasmas at higher energy densities and smaller sizes by operating microplasma configurations at high pressure conditions. We studied the discharge and analyzed its variation with changes in current and pressure. The discharge was analyzed by microscopic visualization and data from the images and was processed to measure the current density and estimate charged particle density. By increasing the pressure beyond 200 psi and by minimizing the discharge current required for sustaining the plasma, we have been able to achieve discharge sizes of 7 mu m in nitrogen and as small as 20 μm in helium. Optical emission spectroscopic studies were carried out to measure gas temperature and vibrational temperature using the nitrogen 2nd positive system. With increase in pressure, the transition from non-equilibrium plasma to equilibrium plasma was also studied using the OES temperature measurements. iv Temperature measurements are also used to estimate normalized current densities. Normalized current density results obtained after introducing the corrected effective pressure based on the increased gas temperature are close to the value of 400 mu A /cm^2*Torr^2 obtained for low pressure normal glow discharges in nitrogen. This research presents further validation of the general operational characteristics of microplasmas being pressure scaled versions of normal glow discharges. Attained energy densities are ten to twenty times higher than in atmospheric pressure microplasmas. Discharge sizes are also significantly smaller, decreasing with increasing pressure, but the scaling is with density ‘nd’ rather than pressure ‘Pd’ due to the increase in gas temperature with pressure, indicating a dependence on collisional processes. We can infer that at higher pressures, the operational characteristics of more complex plasma discharges like dielectric barrier discharges, RF plasmas, etc. follow scaling patterns, transitions and limits similar to the microplasma discharge studied in this thesis.

This study develops and demonstrates a microfluidic module for investigating the mechanism of inorganic fouling caused by the precipitation of calcium sulfate (CaSO4) on nanofiltration membranes. The developed microfluidic module enables sensitive system responses, rapid detection and real time observation of inorganic fouling commonly encountered in water treatment industries. For this development, CaSO4 is selected as the model salt due to its unique fouling characteristics. The effect of the operating conditions, such as pressure and permeate flux, was on the fouling behavior is investigated. A plate-frame type microfluidic chip was fabricated and employed in a dead-end filtration mode for constant-flux fouling experiments. The nanofiltration chip module has a dimension of 50 mm ¡Ñ 25 mm ¡Ñ 12 mm. It is consisted of a polymeric nanofilter, a pressure acquisition unit, a C.C.D., and micro electrodes on the nanofilter for investigating the relationships among trans-membrane pressure, conductivity on membrane surface and permeate fluxes. With the microfluidic system, real-time concentration polarization, bulk nucleation of CaSO4 and surface crystal accumulation were observed in terms of the variations of pressure and conductivity on membrane surface, which were verified with scanning electron micrographs to confirm the corresponding fouling stage. It is found that membrane surface conductivity increases with trans-membrane pressure before bulk crystallization of CaSO4, then slightly decreases after the formation of bulk nuclei due to the removal of solute in the aqueous phase. The conductivity remains relatively constant during cake formation stage while trans-membrane pressure steadily increases. This study successfully integrates microfluidic technology with pressure and electrical measurements for detecting the dynamic transition during CaSO4 fouling, and reports for the first time the experimental measurement of the initiation of inorganic cake formation.

<p>This thesis deals with the problems of scaling aerodynamic data from wind tunnel conditions to free flight. The main challenges when this scaling should be performed is how the model support, wall interference and the potentially lower Reynolds number in the wind tunnel should be corrected.</p><p>Computational Fluid Dynamics (CFD) simulations have been performed on a modern transonic transport aircraft in order to reveal Reynolds number effects and how these should be scaled accurately. This investigation also examined how the European Transonic Wind tunnel (ETW) twin sting model support influences the flow over the aircraft. In order to further examine Reynolds number effects a MATLAB based code capable of extracting local boundary layer properties from structured and unstructured CFD calculations have been developed and validated against wind tunnel measurements. A general scaling methodology is presented.</p>

Thesis (Ed. S.)--Marshall University, 2009. / Title from document title page. Includes abstract. Document formatted into pages: contains 33 p. Includes bibliographical references p. 31-33.

Gas turbine engines are conceptually designed using performance maps that describe the compressor’s effect on the cycle. During the traditional design process, the cycle designer selects a compressor design point based on criteria to meet cycle design point requirements, and performance maps are found or created for off-design analysis that meet this design point selection. Although the maps always have a pedigree to an existing compressor design, oftentimes these maps are scaled to account for design or technology changes. Scaling practices disconnect the maps from the geometry and flow associated with the reference compressor, or the design parameters which are needed for compressor preliminary design. A goal in gas turbine engine research is to bridge this disconnect in order to produce acceptable performance maps that are coupled with compressor design parameters. A new compressor conceptual design and performance prediction method has been developed which will couple performance maps to conceptual design parameters. This method will adapt and combine the key elements of compressor conceptual design with multiple-meanline analysis, allowing for a map of optimal performance that is attached to reasonable design parameters to be defined for cycle design. This method is prompted by the development of multi-fidelity (zooming) analysis capabilities, which allow compressor analysis to be incorporated into cycle analysis. Integrating compressor conceptual design and map generation into cycle analysis will allow for more realistic decisions to be made sooner, which will reduce the time and cost used for design iterations.

This dissertation describes the investigation of the fouling of a reverse osmosis membrane under different operating conditions. A mass transfer model to predict the permeate flux decline is defined. These studies used kaolin clay and bentonite clay as the fouling particles. As the membranes, thin film Low fouling Composite 1 polyamide reverse osmosis flat sheet membranes were used. Baseline experiments using only kaolin in D.I. water were conducted. At an operating pressure of approximately 1,380 kPa, no flux decline was observed. These results established the effects of a membrane-particle interaction. For the fouling experiments with kaolin clay, experiments show a linear relationship between the mass of the deposited foulant layer and total permeate flux decline. The increased concentration of scale forming salts such as calcium chloride and sodium carbonate combined with clay particles has been found to increase flux decline. It also leads to the formation of a less porous cake layer on the membrane surface, which may be due to the particle surface charge. The increase in transmembrane pressure leads to the formation of a well compacted, less porous, cake layer on the membrane surface. The reduced porosity results in the deterioration of the permeate quality, which is a direct result of reduced back diffusion of the salt solution.A fouling model that combines a resistance-in-series model and a simplified-mass-transport relationship were used to predict the transient stage permeate flux of a reverse osmosis membrane. This model contains a constant which is a function of the operating condition and the ionic species in the feed solution. It was found that the results from the model agreed with the experimental results.

A remarkable property of developing organisms is the consistency and robustness within the formation of the body plan. In many animals, morphological pattern formation is orchestrated by conserved signaling pathways, through a process of strict spatio-temporal regulation of cell fate specification. Although morphological patterns have been the focus of both classical and recent studies, little is known about how this robust process is modified throughout evolution to accomodate different morphological adaptations.

In the context of regionalism and regionalisation, the notion of a region holds sway. Discussions around the topic of how spatial entities defined as ‘regions’ form, evolve, develop, become institutionalised and sometimes stabilized have been active and profound over the last forty years. Moreover, rich and diverse literature provides different conceptualizations and problematisation of regions that have been changing over time. ‘Heterogeneous relations’ that stretch over boundaries and are not territorially fixed have been accorded an increased attention in the regional studies. This research investigates the region building process in the Alpine region and analyses different agenda-settings pursued by various stakeholders in the Alpine region. The study employs qualitative methods to analyse processes of region building by applying Paasi’s institutionalisation theory. The findings show the regional dynamics in the case under investigation and claims that the Alpine region has being transformed from a closed, bounded, territorially fixed entity to a relational one, based on not territorially fixed heterogeneous relations. This transformation leads from a relatively ‘fixed’ Alpine region (as defined by Alpine Convention) to a more fluid, unbounded and ‘fuzzy’ space – the Alpine macro-region, which is being developing.

Η παρούσα εργασία εστιάζει στη μελέτη αισθητήρων με χρήση μικροδομημένων οπτικών ινών (ή οπτικών ίνών φωτονικών κρυστάλλων) με δύο πυρήνες, οι οποίοι αλληλεπιδρούν μεταξύ τους. Για την πληρότητα της μελέτης γίνεται αρχικά μια ανασκόπηση των βασικών χαρακτηριστικών των ινών φωτονικών κρυστάλλων όπως οι απώλειες, η διασπορά, και το φαινόμενο της περιοδικής μεταφοράς ενέργειας μεταξύ των πυρήνων σε μία διπύρηνη ίνα φωτονικών κρυστάλλων. Το τελευταίο αποτελεί βάση για τη λειτουργία της ίνας ως αισθητήρα. Στη συνέχεια, αναλύονται τα βασικά χαρακτηριστικά των αισθητήρων μικροδομημένων οπτικών ινών και μελετάται η ευαισθησία συναρτήσει του μήκος κύματος της διαδιδόμενης ακτινοβολίας και των γεωμετρικών χαρακτηριστικών της ίνας. Πιο συγκεκριμένα, μελετάται η ευαισθησία για τρία μοντέλα ινών, με μία, δύο και τρεις οπές μεταξύ των πυρήνων τους. Ως υλικό γεμίσματος των οπών θεωρήθηκε το νερό, διότι είναι ένας από τους πιο κοινούς διαλύτες, κατάλληλος και για βιολογικά δείγματα. Για κάθε ένα από τα παραπάνω μοντέλα εξετάζεται η συμπεριφορά του αισθητήρα συναρτήσει του μήκους κύματος της διαδιδόμενης ακτινοβολίας. Ακολούθως, μελετάται η συμπεριφορά των αισθητήρων όταν υποβληθούν σε μεταβολή κλίμακας (scaling), δηλαδή όταν μεταβληθούν ταυτόχρονα όλες οι γεωμετρικές παράμετροι του αισθητήρα, κρατώντας σταθερές τις αναλογίες. Ο λόγος για τον οποίο γίνεται αυτό είναι διότι αυξάνοντας την διατομή της ίνας αυξάνει παράλληλα η διάμετρος των οπών με αποτέλεσμα να διευκολύνεται το γέμισμά τους με το υπό μελέτη υλικό. Όμως, καθώς αυξάνεται η διατομή της ίνας αυξάνει παράλληλα και η απόσταση μεταξύ των πυρήνων, μειώνοντας έως εξαλείφοντας την αλληλεπίδρασή τους. Για το λόγο αυτό παρουσιάζεται μια βελτιωμένη μορφή του αισθητήρα με κεντρικές οπές στους δύο πυρήνες, με σκοπό το άπλωμα των ρυθμών και κατά συνέπεια την αύξηση της αλληλεπίδρασης μεταξύ των πυρήνων. Κατ’ αυτόν τον τρόπο η μικροδομημένη ίνα μπορεί να λειτουργήσει ως αισθητήρας για σχετικά μεγάλες τιμές της μεγέθυνσης, κάτι που δεν είναι δυνατόν απουσία κεντρικών οπών. Τέλος, παρουσιάζονται αποτελέσματα και για ένα μοντέλο αισθητήρα συμβατικής οπτικής ίνας με δύο πυρήνες και κεντρικές οπές, το οποίο στηρίζεται στην ίδια αρχή λειτουργίας και παρουσιάζει παρόμοια συμπεριφορά με τις διπύρηνες μικροδομημένες ίνες. / This MSc thesis focuses on the study of sensors using microstructured optical fibers (or photonic crystal optical fibers) with two cores, which interact with each other. For the completeness of the study, first is attempted an overview of the basic characteristics of the photonic crystal fiber such as losses, dispersion and the effect of periodic transfer of energy among the cores in a dual core photonic crystal fiber. The latter forms the base for the operation of the fiber as sensing element. Then, the basic characteristics of the sensors using microstructured optical fibers are examined and the sensitivity is studied depending on the wavelength of the propagating radiation and on the geometric characteristics of the fiber. Specifically, the sensitivity of the sensor is studied for three fiber models with one, two and three holes between their cores. Water is assumed as filling material of the holes, since it is one of the most common dissolvers, also suitable for biological samples. For each model the behaviour of the sensor depending on the wavelength of the propagating radiation is studied. Afterwards, the behaviour of the sensor under scaling of the fiber dimensions is studied. In more detail all the geometrical parameters of the sensor are changed simultaneously and proportionally. From a practical point of view increasing the fiber dimensions facilitates the filling of the holes with the material under study. However, the distance between the cores is also increased, reducing or even eliminating their interaction. Therefore, an improved form of the sensor is presented. This form has central holes in the cores in order to extend the spatial overlap of the modes increasing the interaction between the cores. This way, the microstructured fiber can operate as a sensor even for relatively large scaling, which is not possible without central holes. Finally, a conventional model of ordinary dual core optical fiber sensor is studied, having central holes in both cores. It is based on the same principle of operation and has similar behaviour with the dual core microstructured optical fibers.