Heterogeneity in lattice potentials (like random or quasiperiodic) can localize linear, non-interacting waves and halt their propagation. Nonlinearity induces wave interactions, enabling energy exchange and leading to chaotic dynamics. Understanding the interplay between the two is one of the topical problems of modern wave physics. In particular, one questions whether nonlinearity destroys localization and revives wave propagation, whether thresholds in wave energy/norm exist, and what the resulting wave transport mechanisms and characteristics are. Despite remarkable progress in the field, the answers to these questions remain controversial and no general agreement is currently achieved. This thesis aims at resolving some of the controversies in the framework of nonlinear dynamics and computational physics. Following common practice, basic lattice models (discrete Klein-Gordon and nonlinear Schroedinger equations) were chosen to study the problem analytically and numerically. In the disordered linear case all eigenstates of such lattices are spatially localized manifesting Anderson localization, while nonlinearity couples them, enabling energy exchange and chaotic dynamics. For the first time we present a comprehensive picture of different subdiffusive spreading regimes and self-trapping phenomena, explain the underlying mechanisms and derive precise asymptotics of spreading. Moreover, we have successfully generalized the theory to models with spatially inhomogeneous nonlinearity, quasiperiodic potentials, higher lattice dimensions and arbitrary nonlinearity index. Furthermore, we have revealed a remarkable similarity to the evolution of wave packets in the nonlinear diffusion equation. Finally, we have studied the limits of strong disorder and small nonlinearities to discover the probabilistic nature of Anderson localization in nonlinear disordered systems, demonstrating the finite probability of its destruction for arbitrarily small nonlinearity and exponentially small probability of its survival above a certain threshold in energy. Our findings give a new dimension to the theory of wave packet spreading in localizing environments, explain existing experimental results on matter and light waves dynamics in disordered and quasiperiodic lattice potentials, and offer experimentally testable predictions.

This study deals with poly(ether block amide) (PEBA) (type 2533) membranes for gas separation. A new method was developed to prepare flat thin film PEBA membranes by spontaneous spreading of a solution of the block copolymer on water surface. The membrane formation is featured with simultaneous solvent evaporation and solvent exchange with the support liquid, i.e. water. The formation of a uniform and defect-free membrane was affected by the solvent system, polymer concentration in the casting solution and temperature. Propylene separation from nitrogen, which is relevant to the recovery of propylene from the de-gassing off-gas during polypropylene manufacturing, was carried out using flat PEBA composite membranes formed by laminating the aforementioned PEBA on a microporous substrate. The propylene permeance was affected by the presence of nitrogen, and vice versa, due to interactions between the permeating components. Semi-empirical correlations were developed to relate the permeance of a component in the mixture to the pressures and compositions of the gas on both sides of the membrane, and the separation performance at different operating conditions was analyzed in terms of product purity, recovery and productivity on the basis of a cross flow model. To further understand gas permeation behavior and transport mechanism in the membranes, sorption, diffusion, and permeation of three olefins (i.e., C2H4, C3H6, and C4H8) in dense PEBA membranes were investigated. The relative contribution of solubility and diffusivity to the preferential permeability of olefins over nitrogen was elucidated. It was revealed that the favorable olefin/nitrogen permselectivity was primarily attributed to the solubility selectivity, whereas the diffusivity selectivity may affect the permselectivity negatively or positively, depending on the operating temperature and pressure. At a given temperature, the pressure dependence of solubility and permeability could be described empirically by an exponential function. The limiting solubility at infinite dilution was correlated with the reduced temperature of the permeant. The separation of volatile organic compounds (VOCs), which are more condensable than olefin gases, from nitrogen stream by the thin film PEBA composite membranes for potential use in gasoline or other organic vapour emission control was also studied. The membranes exhibited good separation performance for both binary VOC/N2 and multi-component VOCs/N2 gas mixtures. The permeance of N2 in the VOC/N2 mixtures was shown to be higher than pure N2 permeance due to membrane swelling induced by the VOCs dissolved in the membrane. The effects of feed VOC concentration, temperature, stage cut, and permeate pressure on the separation performance were investigated. Additionally, hollow fiber PEBA/polysulfone composite membranes were prepared by the dip coating technique. The effects of parameters involved in the procedure of polysulfone hollow fiber spinning and PEBA layer deposition on the permselectivity of the resulting composite membranes were investigated. Lab scale PEBA hollow fiber membrane modules were assembled and tested for CO2/N2 separation with various flow configurations using a simulated flue gas (15.3% carbon dioxide, balance N2) as the feed. The shell side feed with counter-current flow was shown to perform better than other configurations over a wide range of stage cuts in terms of product purity, recovery and productivity.

This thesis is primarily about the mapping and analyze of the phenomenon of an impinging jet by experimental measurements and numerical simulations by CFD. The mapping shows the characteristics of velocity in and around the impinging jet with different conditions. Additional studies were made by analyzing the pressure along the vertical jet axis, but also weight measurements were part of the investigation. The measurements covered the range from 10 m/s, 20 m/s and 30 m/s, which corresponds to a Reynolds number of 17 000, 34 000 and 50 000. The impinging jet is therefore considered to be highly turbulent. The main difference from previous studies is the use of the ultrasonic anemometer to measure the velocities. These create the ability of measuring the velocities on three coordinates. The jet’s contour was crucial to determine the penetration of ambient air flowing into the jet with an angle of around 88° and the entrainment of the ambient air multiple the jet volume flow. In comparison with CFD, the number of cells in the mesh design and the type of model plays a substantial role. The model k-ε Realized came closest to the experimentally measurements, while the SST k-ω and RNG k-ε EWF had far more entrainment of the ambient air into the impinging jet. / Detta examensarbete handlar om att kartlägga och analysera fenomenet av en ”impinging jet” genom experimentella mätningar samt numeriska simuleringar som CFD. Undersökningen visar karakteristiken av hastigheten i och kring strålen med olika förutsättningar. Kompletterande undersökningar gjordes för trycket i luftstrålens centrum längs den vertikala axeln, men även viktmätningar var del av undersökningen. Mätningarna omfattade hastigheter från 10 m/s, 20 m/s och 30 m/s som motsvarar ett Reynoldstal med 17 000, 34 000 och 50 000. Luftstrålen betraktas därför som turbulent. Det som skiljer sig från tidigare experiment är att hastigheten mättes med en ultrasonic anemometer som egentligen används inom metrologin för att mäta vindhastigheter. Därmed skapades en tredimensionell bild av hastigheten i och kring luftstrålen. Mätområdet sträckte sig från strålens utgångspunkt ner till strax ovanför plattan. Luftstrålens fastställda kontur var avgörande för att bestämma den inträngande omgivningsluften som strömmar in i strålen med en genomsnittlig vinkel av 88°. Denna inströmmande omgivningsluft flerfaldigade strålens volym. I jämförelse med CFD simuleringen visades att antal celler i meshen är avgörande för att skapa liknande och reala förutsättningar. Vid undersökningen av den inträngande omgivningsluften visades även att själva modellen spelar en avgörande roll. Det var modellen k-ε Realized som kom närmast mätningarna. Däremot uppvisade SST k-ω och RNG k-ε EWF modellerna mycket mer inträngande omgivningsluft i jämförelse med mätningarnas resultat.

This study deals with poly(ether block amide) (PEBA) (type 2533) membranes for gas separation. A new method was developed to prepare flat thin film PEBA membranes by spontaneous spreading of a solution of the block copolymer on water surface. The membrane formation is featured with simultaneous solvent evaporation and solvent exchange with the support liquid, i.e. water. The formation of a uniform and defect-free membrane was affected by the solvent system, polymer concentration in the casting solution and temperature. Propylene separation from nitrogen, which is relevant to the recovery of propylene from the de-gassing off-gas during polypropylene manufacturing, was carried out using flat PEBA composite membranes formed by laminating the aforementioned PEBA on a microporous substrate. The propylene permeance was affected by the presence of nitrogen, and vice versa, due to interactions between the permeating components. Semi-empirical correlations were developed to relate the permeance of a component in the mixture to the pressures and compositions of the gas on both sides of the membrane, and the separation performance at different operating conditions was analyzed in terms of product purity, recovery and productivity on the basis of a cross flow model. To further understand gas permeation behavior and transport mechanism in the membranes, sorption, diffusion, and permeation of three olefins (i.e., C2H4, C3H6, and C4H8) in dense PEBA membranes were investigated. The relative contribution of solubility and diffusivity to the preferential permeability of olefins over nitrogen was elucidated. It was revealed that the favorable olefin/nitrogen permselectivity was primarily attributed to the solubility selectivity, whereas the diffusivity selectivity may affect the permselectivity negatively or positively, depending on the operating temperature and pressure. At a given temperature, the pressure dependence of solubility and permeability could be described empirically by an exponential function. The limiting solubility at infinite dilution was correlated with the reduced temperature of the permeant. The separation of volatile organic compounds (VOCs), which are more condensable than olefin gases, from nitrogen stream by the thin film PEBA composite membranes for potential use in gasoline or other organic vapour emission control was also studied. The membranes exhibited good separation performance for both binary VOC/N2 and multi-component VOCs/N2 gas mixtures. The permeance of N2 in the VOC/N2 mixtures was shown to be higher than pure N2 permeance due to membrane swelling induced by the VOCs dissolved in the membrane. The effects of feed VOC concentration, temperature, stage cut, and permeate pressure on the separation performance were investigated. Additionally, hollow fiber PEBA/polysulfone composite membranes were prepared by the dip coating technique. The effects of parameters involved in the procedure of polysulfone hollow fiber spinning and PEBA layer deposition on the permselectivity of the resulting composite membranes were investigated. Lab scale PEBA hollow fiber membrane modules were assembled and tested for CO2/N2 separation with various flow configurations using a simulated flue gas (15.3% carbon dioxide, balance N2) as the feed. The shell side feed with counter-current flow was shown to perform better than other configurations over a wide range of stage cuts in terms of product purity, recovery and productivity.

Ad hoc networks and bluetooth systems operating over the unlicensed ISM band are in-stances of decentralized wireless networks. By definition, a decentralized network is com-posed of separate transmitter-receiver pairs where there is no central controller to assign the resources to the users. As such, resource allocation must be performed locally at each node. Users are anonymous to each other, i.e., they are not aware of each other's code-books. This implies that multiuser detection is not possible and users treat each other as noise. Multiuser interference is known to be the main factor that limits the achievable rates in such networks particularly in the high Signal-to-Noise Ratio (SNR) regime. Therefore, all users must follow a distributed signaling scheme such that the destructive effect of interference on each user is minimized, while the resources are fairly shared. In chapter 2 we consider a decentralized wireless communication network with a fixed number of frequency sub-bands to be shared among several transmitter-receiver pairs. It is assumed that the number of active users is a realization of a random variable with a given probability mass function. Moreover, users are unaware of each other's codebooks and hence, no multiuser detection is possible. We propose a randomized Frequency Hopping (FH) scheme in which each transmitter randomly hops over a subset of sub-bands from transmission slot to transmission slot. Assuming all users transmit Gaussian signals, the distribution of the noise plus interference is mixed Gaussian, which makes calculation of the mutual information between the transmitted and received signals of each user intractable. We derive lower and upper bounds on the mutual information of each user and demonstrate that, for large SNR values, the two bounds coincide. This observation enables us to compute the sum multiplexing gain of the system and obtain the optimum hopping strategy for maximizing this quantity. We compare the performance of the FH system with that of the Frequency Division (FD) system in terms of the following performance measures: average sum multiplexing gain and average minimum multiplexing gain per user. We show that (depending on the probability mass function of the number of active users) the FH system can offer a significant improvement in terms of the aforementioned measures. In the sequel, we consider a scenario where the transmitters are unaware of the number of active users in the network as well as the channel gains. Developing a new upper bound on the differential entropy of a mixed Gaussian random vector and using entropy power inequality, we obtain lower bounds on the maximum transmission rate per user to ensure a specified outage probability at a given SNR level. We demonstrate that the so-called outage capacity can be considerably higher in the FH scheme than in the FD scenario for reasonable distributions on the number of active users. This guarantees a higher spectral efficiency in FH compared to FD. Chapter 3 addresses spectral efficiency in decentralized wireless networks of separate transmitter-receiver pairs by generalizing the ideas developed in chapter 2. Motivated by random spreading in Code Division Multiple Access (CDMA), a signaling scheme is introduced where each user's code-book consists of two groups of codewords, referred to as signal codewords and signature codewords. Each signal codeword is a sequence of independent Gaussian random variables and each signature codeword is a sequence of independent random vectors constructed over a globally known alphabet. Using a conditional entropy power inequality and a key upper bound on the differential entropy of a mixed Gaussian random vector, we develop an inner bound on the capacity region of the decentralized network. To guarantee consistency and fairness, each user designs its signature codewords based on maximizing the average (with respect to a globally known distribution on the channel gains) of the achievable rate per user. It is demonstrated how the Sum Multiplexing Gain (SMG) in the network (regardless of the number of users) can be made arbitrarily close to the SMG of a centralized network with an orthogonal scheme such as Time Division (TD). An interesting observation is that in general the elements of the vectors in a signature codeword must not be equiprobable over the underlying alphabet in contrast to the use of binary Pseudo-random Noise (PN) signatures in randomly spread CDMA where the chip elements are +1 or -1 with equal probability. The main reason for this phenomenon is the interplay between two factors appearing in the expression of the achievable rate, i.e., multiplexing gain and the so-called interference entropy factor. In the sequel, invoking an information theoretic extremal inequality, we present an optimality result by showing that in randomized frequency hopping which is the main idea in the prevailing bluetooth devices in decentralized networks, transmission of independent signals in consecutive transmission slots is in general suboptimal regardless of the distribution of the signals. Finally, chapter 4 addresses a decentralized Gaussian interference channel consisting of two block-asynchronous transmitter-receiver pairs. We consider a scenario where the rate of data arrival at the encoders is considerably low and codewords of each user are transmitted at random instants depending on the availability of enough data for transmission. This makes the transmitted signals by each user look like scattered bursts along the time axis. Users are block-asynchronous meaning there exists a delay between their transmitted signal bursts. The proposed model for asynchrony assumes the starting point of an interference burst is uniformly distributed along the transmitted codeword of any user. There is also the possibility that each user does not experience interference on a transmitted codeword at all. Due to the randomness of delay, the channels are non-ergodic in the sense that the transmitters are unaware of the location of interference bursts along their transmitted codewords. In the proposed scheme, upon availability of enough data in its queue, each user follows a locally Randomized Masking (RM) strategy where the transmitter quits transmitting the Gaussian symbols in its codeword independently from symbol interval to symbol interval. An upper bound on the probability of outage per user is developed using entropy power inequality and a key upper bound on the differential entropy of a mixed Gaussian random variable. It is shown that by adopting the RM scheme, the probability of outage is considerably less than the case where both users transmit the Gaussian symbols in their codewords in consecutive symbol intervals, referred to as Continuous Transmission (CT).

The interaction of a bubble with solid surfaces, hydrophobic and hydrophilic, was investigated. When a bubble approaches towards a solid surface, a thin liquid film forms between them. The liquid in the film drains until an instability forms and film ruptures resulting in a three phase contact (TPC). Following rupture, the TPC line spreads on the solid surface. In the present study, glycerol-water solutions with varying percentages of water were used to investigate the effect of viscosity. Experiments were carried out with varying bubble size. The rupture and TPC line movement were recorded by high-speed digital video camera. The dependence of the TPC line movement on different parameters was investigated. The experimental results were compared with the existing theories for the TPC line movement. An empirical equation was developed to predict the TPC line movement. Formation or rupturing of the intervening film in case of a hydrophilic surfaces, which were glass surface cleaned by six cleaning techniques, was investigated. It was shown that a stable film forms for acid or alkali cleaning.

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Title from PDF of title page. / Document formatted into pages; contains 105 pages. / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Relative plate motion history since 30 Ma between the Pacific and the southern portion of the Nazca (Farallon) plates is examined. The history is constrained by available seafloor magnetic anomaly data and a two-minute grid of predicted bathymetry derived from satellite altimetry and shipboard sensors. These data are used to create a new plate motion reconstruction based on new magnetic anomaly identifications and finite poles of motion. The new identified magnetic isochrons and tectonic reconstruction provides greater resolution to the tectonic history between chrons 7y (24.73 Ma) and 3 (4.18 Ma) than previous interpretations. Shipboard magnetics and aeromagnetic data from over 250 expeditions were plotted and used to extrapolate magnetic anomalies picked from 2D magnetic modeling from selected cruises. Magnetic anomalies were further constrained by tectonic features evident in the predicted bathymetry. / ABSTRACT: Previously published magnetic anomaly locations consistent with this work were used where interpretation could not be constrained by 2D modeling and map extrapolation. Point locations for anomalies were used as input for calculation of finite poles of motion for chrons 10y, 7y, 6c, 5d, 5b, 5aa, 5o, 4a and 3a. An iterative process of anomaly mapping, pole calculation and anomaly point rotations was used to refine the finite poles of motion. Eleven stage poles were calculated from the nine finite poles from this study and two published instantaneous Euler vectors. Tectonic reconstructions indicate a history dominated by two major southward ridge propagation events, the first starting by 28 Ma and completed by 18 Ma. The second event initiated in association with breakup of the Farallon plate around 24 Ma and ceased by about 11 Ma. Lithosphere was transferred from Nazca to Pacific during the first event and in the opposite sense during the second. / ABSTRACT: Development of the Mendoza microplate east of the later propagator occurred at about 20 Ma and this dual spreading process appears to have lasted until about 15 Ma. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Drainage methods for liquefaction remediation have been in use since the 1970's and have traditionally included stone columns, gravel drains, and more recently prefabricated vertical drains. The traditional drainage techniques such as stone columns and gravel drains rely upon a combination of drainage and densification to mitigate liquefaction and thus, the improvement observed as a result of these techniques cannot be ascribed solely to drainage. Therefore, uncertainty exists as to the effectiveness of pure drainage, and there is some hesitancy among engineers to use newer drainage methods such as prefabricated vertical drains, which rely primarily on drainage rather than the combination of drainage and densification. Additionally, the design methods for prefabricated vertical drains are based on the design methods developed for stone columns and gravel drains even though the primary mechanisms for remediation are not the same. The objectives of this research are to use physical and numerical models to assess the effectiveness of drainage as a liquefaction remediation technique and to identify the controlling behavioral mechanisms that most influence the performance of sites treated with prefabricated vertical drains. In the first part of this research, a suite of three large-scale dynamic centrifuge tests of untreated and drain-treated sloping soil profiles was performed. Acceleration, pore pressure, and deformation data was used to evaluate the effectiveness of drainage in reducing liquefaction-induced lateral deformations. The results showed that the drains reduced the generated peak excess pore pressures and expedited the dissipated of pore water pressures both during and after shaking. The influence of the drains on the excess pore pressure response was found to be sensitive to the characteristics of the input motion. The drainage resulted in a 30 to 60% reduction in the horizontal deformations and a 20 to 60% reduction in the vertical settlements. In the second part of this research, the data and insights gained from the centrifuge tests was used to develop numerical models that can be used to investigate the factors that most influence the performance of untreated and drain-treated lateral spread sites. Finite element modeling was performed using the OpenSees platform. Three types of numerical models were developed - 2D infinite slope unit cell models of the area of influence around a single drain, 3D infinite slope unit cell models of the area of influence around a single drain, and a full 2D plane strain model of the centrifuge tests that included both the untreated and drain-treated slopes as well as the centrifuge container. There was a fairly good match between the experimental and simulated excess pore pressures. The unit cell models predicted larger horizontal deformations than were observed in the centrifuge tests because of the infinite slope geometry. Issues were identified with the constitutive model used to represent the liquefiable sand. These issues included a coefficient of volumetric compressibility that was too low and a sensitivity to low level accelerations when the stress path is near the failure surface. In the final part of this research, the simulated and experimental data was used to examine the relationship between the generated excess pore water pressures and the resulting horizontal deformations. It was found that the deformations are directly influenced by both the excess pore pressures and the intensity of shaking. There is an excess pore pressure threshold above which deformations begin to become significant. The horizontal deformations correlate well to the integral of the average excess pore pressure ratio-time history above this threshold. They also correlate well to the Arias intensity and cumulative absolute velocity intensity measures. / text

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