This paper explores the effect of internet market and merchant characterics. Product retail price is not only a major revenue-driven factor for the seller, but also a key decision factor for the buyer. This research investigates how online retailing prices are affected by maket types and merchant characteristics. A dataset of 3,811 retail price quotes collected from 245 product items at 14 categoris from 880 onlline shopping or auction merchants is collected and analyzed. Major findings are below: 1. The average prices in the B2C market are significant higher than that in the C2C markets. No significant price difference is found between C2C markets that charge fees and free C2C markets. These implies that the auction market reduces product prices but whether the market maker charge service fees has no effect on product pricing. 2. Competitive intensity of a market is found to have significant positive effect on the price dispersion rate. This is consistent with prior research findings but is in conflict with the signle price theory in economics. This is because some vendors may intentionally lower their prices to attract customers, which results in a higher dispersion rate. 3. The reputation of a merchant has significant positive effects on its price dispersion in the B2C market. In auction markets, reputation has positive effect on price dispersion in the higher range, but has negative effect in the lower range. In both markets, merchant size has a positive effect on price dispersion in both markets. 4. Finally, price dispersion and effect of market types and product characteristics vary for different product categories.

Agitated dispersions of one liquid in another immiscible liquid are widely used in chemical industry in operations such as liquid-liquid extraction, suspension polymerisation, and blending of polymers. When holdup of the dispersed phase is increased, in an effort to increase the productivity, at a critical holdup, the dispersed phase catastrophically becomes the continuous phase and vice versa. This phenomenon is known as phase inversion. Although the inversion phenomenon has been studied off and on over the past few decades, the mechanism of phase inversion (PI) has yet not become clear. These studies have however brought out many interesting aspects of PI, besides unravelling the effect of physical and operational variables on PL Experiments show that oil-in-water (o/w) and water-in-oil (w/o) dispersions behave very differently, e.g water drops in w/o dispersions contain oil droplets in them, but oil drops in o/w dispersions contain none, dispersed phase hold up at which inversion occurs increases with agitation speed for w/o dispersions but decreases for o/w dispersions. A common feature of both types of dispersions however is that as agitation speed is increased to high values, inversion holdups reach a constant value. A further increase in agitation speed does not change inversion hold up. Although this finding was first reported a long time ago, the implications it may have not received any attentions. In fact, the work reported in the literature since then does not even mention it. The present work shows that this finding has profound implications. Starting with the finding that at high agitation speed inversion hold up does not change with agitation speed, the present work shows that inversion hold up also does not change with agitator diameter, type of agitator and vessel diameter. In these experiments, carried out in agitated vessel, energy was introduced as a point source. The experiments carried out with turbulent flow in annular region of two coaxial cylinders, inner one rotating, in which energy is introduced nearly uniformly throughout the system, show that the inversion holdup remains unchanged. These results indicate that constant values of inversion holdups for a given liquid-liquid systems (o/w and w/o) are properties of the liquid-liquid systems alone, independent of geometrical and operational parameters. A new hypothesis is proposed to explain the new findings. Phase inversion is considered to occur as a result of imbalance between breakup and coalescence of drops. Electrolytes, which affect only coalescence of drops, were therefore added to the system to investigate the effect of altering coalescence of drops on phase inversion. The experiments performed in the presence of electrolyte KI at various concentrations indicate that addition of electrolyte increases the inversion holdup for both o/w and w/o dispersions for three types of systems: non polar-water, polar-water and immiscible organic-organic. Higher the concentration of electrolyte used, higher was the holdup required for phase inversion. These findings indicate that while the addition of electrolyte increases coalescence of drops in lean dispersions, it has exactly opposite effect on imbalance of breakage and coalescence of drops at high holdups near phase inversion point. The opposite effect of electrolytes in lean and concentrated dispersions could be explained qualitatively, but only in part in the light of a new theory, involving multi-particle interactions. The phase inversion phenomenon is quantified in a simple manner by testing the breakage and coalescence rate expressions available in literature. It has been found that, equilibrium drop size (where breakage and coalescence events are in dynamic equilibrium) approaches infinity near phase inversion holdup which is not an ex perimentally observed fact. To capture the catastrophic nature of phase inversion, two steady state approach is proposed. The two steady states namely the stable steady state and unstable steady state, are achieved by modifying the expression for coalescence frequency on the basis of (i) shear coalescence mechanism and, (ii) recognising the fact that at high dispersed phase holdup the droplets are already in contact with each other at all times and hence rendering the second order coales cence process to a first order one. Using two steady states approach, catastrophic phase inversion is shown to occur at finite drop size.

Die chromatische Dispersion ist in optischen Übertragungssystemen mit Datenraten von 10 Gbit/s und darüber einer der Faktoren, der die Länge der Übertragungsstrecke limitiert. Der Hauptteil der chromatischen Dispersion wird in solchen Übertragungssystemen in der Regel durch Dispersionskompensationsfasern ausgeglichen. Aufgrund von z.B. Umwelteinflüssen kann allerdings auch eine sich zeitlich ändernde Dispersion auftreten. Zur Eliminierung dieser Restdispersion wurden unterschiedliche Ansätze wie abstimmbare Faser-Bragg-Gitter, Virtually-Imaged-Phased-Arrays und Delay-Line-Filter publiziert. Delay-Line-Filter, deren periodisches Übertragungsverhalten durch die Filterkoeffizienten bestimmt wird, wurden bereits als Ring-Resonatoren und kaskadierte Mach-Zehnder-Interferometer in integriert-optischer Technologie hergestellt. Integriert-optische Komponenten verursachen aufgrund der Ankopplung an die Fasern des Übertragungssystems hohe Einfügeverluste. Darüber hinaus treten hohe Wellenleiterverluste, polarisationsabhängige Verluste und Polarisationsmodendispersion auf. Daher wird in dieser Arbeit die Realisierung faseroptischer Delay-Line-Filter, die auf faseroptischen Schmelzkopplern und faseroptischen Gewichtungselementen basieren, untersucht. Aufgrund der geometrischen Längen der faseroptischen Schmelzkoppler und der Größe der Gewichtungselemente können solche Filter allerdings nur mit einer geringen Filterordnung und mit einer geringen Anzahl von Gewichtungselementen hergestellt werden. Um mit Filtern niedriger Ordnung eine möglichst effektive Kompensation der Restdispersion zu erzielen, ist zunächst eine sorgfältige Untersuchung der Filtereigenschaften und des Filterentwurfs erforderlich. Durch systematische Untersuchung des Verhaltens der Filterdispersion in Abhängigkeit der Filterkoeffizienten wurden in dieser Arbeit hierzu erstmalig einfache Entwurfsregeln aufgestellt, die für Filter beliebiger Filterordnung zu annähernd konstantem Dispersionsverlauf führen. Auf dieser Grundlage konnte ein faseroptisches Delay-Line-Filter realisiert werden, das auf zwei in Reihe geschalteten faseroptischen 3x3 Schmelzkopplern basiert. Die Dispersion dieses Filters ist in einem Bereich von 50 GHz um die Mitte einer Filterperiode herum annähernd konstant und kann in einem Bereich von +/-50 ps/nm durch ein einzelnes thermisches Gewichtungselement abgestimmt werden. Aufgrund der faseroptischen Realisierung kann die Komponente problemlos in optische Übertragungsstrecken integriert werden und verursacht dabei Einfügeverluste von lediglich 3 dB. In Übertragungsexperimenten bei Datenraten von 42,5 Gbit/s konnte gezeigt werden, dass das Filter in der Lage ist die Dispersionstoleranz des Systems annähernd zu verdoppeln. Dies gilt sowohl für die Kompensation eines einzelnen Kanals als auch für die simultane Kompensation mehrerer benachbarter Übertragungskanäle mit je 42,5 Gbit/s. / Chromatic dispersion is a limiting factor in fast optical networks with channel bit rates of 10 Gbit/s or higher. The main part of the dispersion is usually compensated by spans of dispersion compensating fiber that have a fixed dispersion value. But the residual dispersion caused by environmental changes or rerouting has to be compensated adaptively. To overcome the effects of residual dispersion several approaches like tunable fiber Bragg gratings, virtually imaged phased arrays and delay line filters can be found in literature. The use of delay line filters like cascaded ring-resonators, multi-cavity etalons and cascaded Mach-Zehnder interferometers, whose periodic transfer behavior is determined by their coefficients, have already been developed in planar-optics. These components cause insertion loss due to the coupling to the fibers. Furthermore they suffer from high waveguide loss, non-negligible polarization dependent loss and polarization mode dispersion. In this thesis the realization of tunable delay line filters based on fiberoptic couplers and fiberoptic weighting elements is investigated. Due to the size of these components the filters can be realized with a limited order and a limited number of weighting elements, only. To fulfill these requirements a careful investigation of the filter design is necessary. By systematically investigating the dispersion of the filter depending on the filter coefficients simple design rules for non-recursive delay line filters with approximately constant dispersion are figured out. That enables the realization of a fiberoptic delay line filter, based on two 3x3 couplers concatenated in series. The dispersion of this filter is constant in a bandwidth of about 50 GHz around the center of a period and can be tuned in a range of +/-50 ps/nm by changing one single weighting element. Due to its nature this device causes low loss and can be easily integrated in an optical transmission system. In experiments it was demonstrated that by adding this filter to a 42.5 Gb/s transmission system the +/- 55 ps/nm dispersion tolerance of the optical receiver can almost be doubled - either in a single channel as well as in a multi channel configuration with five adjacent 42.5 Gb/s channels.

Neben der Ausbreitungsgeschwindigkeit ist die Absorption elektromagnetischer Wellen der wichtigste Parameter für die Bearbeitung und Interpretation von Georadar-Daten. Für die realitätsnahe Beschreibung der Ausbreitung elektromagnetischer Wellen in Gesteinen eignet sich das Modell mit konstantem Q und einem Dispersionsansatz der Phasengeschwindigkeit nach Futterman (1982). Anhand von Modellrechnungen wird die Wirkung dieser Parameter auf Wavelets untersucht. Die Ermittlung des absorptionscharakterisierenden Gütefaktors Q aus GPR-Transmissionsdaten erfolgt auf der Basis einer Erweiterung der Q-Definition. Die dazu benutzte Referenzfrequenz fR ist eine Potenzfunktion von zu vergleichenden Amplitudendichten der entsprechenden Äquivalenzspektren. Die Anwendbarkeit der danach benannten Methode der Äquivalenten Bandbreite wird sowohl an synthetischen Daten als auch an Messergebnissen nachgewiesen, die an einem Sandsteinblock sowie an anstehendem Gneis erhalten worden sind. Es werden Möglichkeiten aufgezeigt, Querbeziehungen zwischen Q-Werten und petrophysikalischen Parametern herzustellen.

Delivery of protein therapeutics is restricted to intravenous infusions due to protein-dependent problems including low solubilities, high viscosities, and physical instabilities. The ability to inject high concentrations of proteins via subcutaneous injections would increase accessibility and compliance. Large particles of a protein in a non-aqueous solvent can decrease the viscosity over a solution of equally concentrated individual protein molecules. The lower viscosity of a particle suspension is due to decreased surface area resulting in reduced electroviscous effects, solvation and deviations of the particle shape from a spherical geometry. Additional studies show that aqueous-based dispersions of antibody nanoclusters can be formed by increasing the attractive interactions between protein molecules using the excluded volume effects of extrinsic crowding agents. These novel, equilibrium, nanoclusters are maintained by a balance of highly attractive interactions and weak electrostatic repulsive interactions near the protein’s pI. These protein nanoclusters are ideal for subcutaneous delivery as they have low interactions between the colloids, are reversible in nature, and dissolve rapidly upon dilution in a buffer media. Through in vivo mouse studies, the bioavailability of a monoclonal antibody in the dispersion is prolonged and higher doses can be administered versus a solution. Overall, these studies with high concentration, low viscosity subcutaneous injections of protein therapeutics open new opportunities in biotechnology. For oral delivery of itraconzole, controlled flocculation of individual polymerically-stabilized nanoparticles is used to increase supersaturation. Flocculation of these nanoparticles is achieved by desolvating the polymer by changing the pH. The flocculated dispersions can then be easily filtered. The final amorphous powder maintains high supersaturation with simulated stomach and small intestine conditions and improves bioavailability of itraconazole, over the commercial product, Sporanox®. / text

Flow and transport phenomena in the subsurface often span a wide range of length (nanometers to kilometers) and time (nanoseconds to years) scales, and frequently arise in applications of CO₂ sequestration, pollutant transport, and near-well acid stimulation. Reliable field-scale predictions depend on our predictive capacity at each individual scale as well as our ability to accurately propagate information across scales. Pore-scale modeling (coupled with experiments) has assumed an important role in improving our fundamental understanding at the small scale, and is frequently used to inform/guide modeling efforts at larger scales. Among the various methods, there often exists a trade-off between computational efficiency/simplicity and accuracy. While high-resolution methods are very accurate, they are computationally limited to relatively small domains. Since macroscopic properties of a porous medium are statistically representative only when sample sizes are sufficiently large, simple and efficient pore-scale methods are more attractive. In this work, two Eulerian pore-network models for simulating single-phase flow and solute transport are developed. The models focus on capturing two key pore-level mechanisms: a) partial mixing within pores (large void volumes), and b) shear dispersion within throats (narrow constrictions connecting the pores), which are shown to have a substantial impact on transverse and longitudinal dispersion coefficients at the macro scale. The models are verified with high-resolution pore-scale methods and validated against micromodel experiments as well as experimental data from the literature. Studies regarding the significance of different pore-level mixing assumptions (perfect mixing vs. partial mixing) in disordered media, as well as the predictive capacity of network modeling as a whole for ordered media are conducted. A mortar domain decomposition framework is additionally developed, under which efficient and accurate simulations on even larger and highly heterogeneous pore-scale domains are feasible. The mortar methods are verified and parallel scalability is demonstrated. It is shown that they can be used as “hybrid” methods for coupling localized pore-scale inclusions to a surrounding continuum (when insufficient scale separation exists). The framework further permits multi-model simulations within the same computational domain. An application of the methods studying “emergent” behavior during calcite precipitation in the context of geologic CO₂ sequestration is provided. / text

Nonlinear site response analyses are generally preferred over equivalent linear analyses for soft soil sites subjected to high-intensity input ground motions. However, both nonlinear and equivalent linear analyses often result in large induced shear strains (3-10%) at soft sites, and these large strains may generate unusual characteristics in the predicted surface ground motions. One source of the overestimated shear strains may be attributed to unrealistically low shear strengths implied by commonly used modulus reduction curves. Therefore, modulus reduction and damping curves can be modified at shear strains greater than 0.1% to provide a more realistic soil model for site response. However, even after these modifications, nonlinear and equivalent linear site response analyses still may generate unusual surface acceleration time histories and Fourier amplitude spectra at soft soil sites when subjected to high-intensity input ground motions. As part of this work, equivalent linear and nonlinear 1D site response analyses for the well-known Treasure Island site demonstrate the challenges associated with accurately modeling large shear strains, and subsequent surface response, at soft soil sites. Accounting for the uncertainties associated with the shear wave velocity profile is an important part of a properly executed site response analyses. Surface wave data from Grenoble, France and Mirandola, Italy have been used to determine shear wave velocity (Vs) profiles from inversion of surface wave data. Furthermore, Vs profiles from inversion have been used to determine boundary, median and statistically-based randomly generated profiles. The theoretical dispersion curves from the inversion analyses as well as the boundary, median and randomly generated Vs profiles are compared with experimentally measured surface wave data. It is found that the median theoretical dispersion curve provides a satisfactory fit to the experimental data, but the boundary type theoretical dispersion curves do not. Randomly generated profiles result in some theoretical dispersion curves that fit the experimental data, and many that do not. Site response analyses revealed that the greater variability in the response spectra and amplification factors were determined from the randomly generated Vs profiles than the inversion or boundary Vs profiles.

Not available / text

This dissertation first develops a theoretical framework to enable the estimation of cost efficiency and conduct parameter without total cost data. By validating this framework using U.S. airline data, this dissertation shows the feasibility of the theoretical framework. Based on the estimates of marginal cost efficiency and conduct parameter, this dissertation also finds some support for the Quiet Life Hypothesis. In Chapter III, this dissertation analyzes the determinants for price dispersion, especially conduct parameter and cost efficiency. Generally speaking, we find negative relationship between conduct parameter and price dispersion and negative relationship between marginal cost efficiency and price dispersion. In Chapter IV, this thesis examines the dynamics that lead to high price dispersion. To be more specific, this thesis concentrates on advanced days purchased and load factor.

The use of solid dispersions to formulate poorly water soluble drugs is a growing field in the pharmaceutical sciences. Hot-melt extrusion is a common method for producing dispersions. However, bench-top extruders require large amounts of powder to run and are inappropriate for early formulation screens. Plastic and glass syringes are readily available in most laboratories. 250 mg of drug-polymer blend is placed in a plastic syringe body that has the tip covered with a bent needle. The syringe is heated for 5 minutes and the extrudate is pushed through the syringe. Extrudates are characterized by differential scanning calorimetry and powder x-ray diffraction. Acetaminophen, griseofulvin, indomethacin, salicylamide, and sulfamethoxazole extruded with polyvinylpyrrolidone K12 match or exceed the performance of solvent evaporated controls. Glass syringes can be used when polymers have processing ranges above the melting point of the plastic syringes. Syringe extrusion is effectively demonstrated as a rapid process for early formulation screening.