Experimental and computational study of multiphase flow in dry powder inhalers

Dry Powder Inhalers (DPIs) have great potential in pulmonary drug delivery; the granular powder, used as active ingredient in DPIs, is ozone friendly and the operation of DPIs ensures coordination between dose release and patient inhalation. However, the powder fluidisation mechanisms are poorly understood which leads to low efficiency of DPIs with 10-35 % of the dose reaching the site of action. The main aim of this thesis is to study the hydrodynamics of powder fluidisation in DPIs, using experimental and computational approaches. An experimental test rig was developed to replicate the process of transient powder fluidisation in an impinging air jet configuration. The powder fluidisation chamber was scaled up resulting in a two dimensional particle flow prototype, which encloses 3.85 mm glass beads. Using optical image processing techniques, individual particles were detected and tracked throughout the experimental time and domain. By varying the air flow rate to the test section, two particle fluidisation regimes were studied. In the first fluidisation regime, the particle bed was fully fluidised in less than 0.25 s due to the strong air jet. Particle velocity vectors showed strong convective flow with no evidence of diffusive motion triggered by inter-particle collisions. In the second fluidisation regime, the particle flow experienced two stages. The first stage showed strong convective flow similar to the first fluidisation regime, while the second stage showed more complex particle flow with collisional and convective flow taking place on the same time and length scales. The continuum Two Fluid Model (TFM) was used to solve the governing equations of the coupled granular and gas phases for the same experimental conditions. Sub-models for particle-gas and particle-particle interactions were used to complete the model description. Inter-particle interactions were resolved using models based on the kinetic theory of granular flow for the rapid flow regime and models based on soil mechanics for the frictional regime. Numerical predictions of the first fluidisation regime showed that the model should incorporate particle-wall friction and minimise diffusion, simultaneously. Ignoring friction resulted in fluidisation timing mismatch, while increasing the diffusion resulted in homogenous particle fluidisation in contrast to the aggregative convective fluidisation noticed in the experiments. Numerical predictions of the second fluidisation regime agreed well with the experiments for the convection dominated first stage of flow up to 0.3 s. However, later stages of complex particle flow showed qualitative discrepancies between the experimental and the computational approaches suggesting that current continuum granular models need further development. The findings of the present thesis have contributed towards better understanding of the mechanics of particle fluidisation and dense multiphase flow in DPI in particular, and particle bed fluidisation using impinging air jet in general. The use of TFM for predicting high speed convective granular flows, such as those in DPIs, is promising. Further studies are needed to investigate the form of particle-particle interactions within continuum granular flow models

Visualization of Some Energy Levels of Even-Even Nuclei

The properties of the lowest excited states of atomic nuclei offer a very sensitive test for nuclear structure theories. To identify and distinguish the shape phase transitions, one needs the variation behaviors of the energy ratios with respect to the neutron or proton number of the nuclei. The possibility of generating images of the variation behaviors of energy levels and energy ratios by exploiting the large body of data on stable and near-stable nuclei, whose accumulation over the past decades now permits, prompted us to produce this atlas which illustrates in a simple and effective way these behaviors. The atlas represents the experimental data of the energy levels and energy ratios of the 2_1^+, 4_1^+, 2_2^+ and 4_2^+ states of 645 even-even nuclei. The interpolation surfaces of the values of energy levels and energy ratios, E(2,1+), E(2,2+), E(4,1+), E(4,2+), E(4,1+)/E(2,1+), E(4,2+)/E(2,2+), E(2,2+)/E(2,1+), E(4,2+)/E(4,1+), E(4,2+)/E(2,1+) and E(4,1+)/E(2,2+), through all points of the even-even nuclear landscape are presented. The variation of these values with respect to each chain of isotopes and isotones are displayed using two-dimensional figures. Visualization of the data through visual imagery has been considered an effective way for connecting abstract and concrete ideas as well as allowing the emergence of the significant patterns. Moreover, we will see that it is possible, in many if not most cases, to understand the detailed results of complex calculations of the nuclear structure theories with an absolute minimum of formalism and often by inspection. The introduction of this atlas contains a brief account of some topics of present-day interest in theoretical nuclear structure. These topics can be used to explain the existence of a few typical patterns of nuclear spectra as well as some of the systematic changes in these patterns over sequences of nuclei. Researchers working on nuclear theory will find this atlas handy to understand the nuclear structure theories

An Electrodynamics Solver for Moving Sources

An Electrodynamics solver for moving sources is introduced. The main challenges and formulation are highlighted. The solver enables the simulation of fields for sources undergoing arbitrary motion. Two examples of uniformly moving current sources are provided to correlate the numerical solver computations with theory, based on the solution of Maxwell's equations and the relativistic transformation of the electromagnetic fields

Synthesis and Characterization of Some Conducting Polymers and Their Complexed Compounds

The chemical co-polymerization of aniline with o-anthranilic acid (AA) to form copolymer films has been made in aqueous hydrochloric acid medium. Poly vinylcarbazole (PVK) was prepared by free radical mechanism. The copolymer (AA) and polymer (PVK) were reacted with KI respectively, to produce a complex compounds. Also, the complex of copolymer (AA) with NaOEt was prepared. The conductivity, IR spectra and the thermal gravimetric analysis of these polymers and their complexes were measured and discussed. It was found that, the specific electrical conductivity (σ) of the copolymer (AA) in presence of NaOEt increases with increase in temperature, whereas decreases with complex of copolymer (AA) +KI. The electrical properties of the PVK were enhanced upon reacting it with KI

Energetic and Thermodynamic Analysis of Adsorption Isotherm Type VI of Xenon on Graphite Nanotubes

New theoretical expressions for the modeling of adsorption isotherms of Xenon on Graphite at 110 K have been established. The establishment of these new expressions is based on statistical physics formalism and some working assumptions. This method allowed estimation of physico-chemical parameters in the theoretical model. The parameters intervening in the adsorption process have been deduced directly from experimental adsorption isotherm by numerical simulation. The proposed models allow a good correlation to Type VI experimental isotherms. We mainly introduce three parameters affecting the adsorption process, namely, the density of Xenon receptor sites NM, the number of molecules per site n and the Xenon adsorption energy. Then we apply the model to calculate thermodynamics functions which govern the adsorption mechanism such as entropy, free enthalpy and internal energy