Hydrodynamics and mass transfer processes associated with the absorption of oxygen in liquid films flowing across a rotating disc

PhD Thesis (Multimedia items accompanying this thesis to be consulted at Robinson Library)This study is concerned with mass transfer to a liquid film as it flows across the surface of a rotating disc, and in particular with the absorption of oxygen into films of water. The primary aim of the study was the measurement of the distribution of oxygen concentration across the disc radius, for a wide range of liquid flowrates, rotational speeds, and the comparison of these distributions with those resulting from a range of theoretical models of this process. These comparisons, and the observation that with flow and rotary speeds of practical interest, the liquid films invariably exhibit characteristic surface waves indicate the importance of this hydrodynamic condition with respect to the mass transfer process. --3 The main dimensionless variables which are influential in describing flow on the disc have been identified, and used in the formulation of satisfactory mass transfer design equation.The Robert Wood Fellowship

Monitoring the strength gain of structural adhesives using the electromechanical impedance technique: An experimental investigation

Structural adhesives are employed to externally bond fibre-reinforced polymer (FRP) composites onto concrete structures for repair and strengthening purposes. The strength development of the bond layer is important to ensure the overall performance of the FRP-strengthened system. The non-destructive piezoelectric-based monitoring technique, namely the electromechanical impedance (EMI) technique, is introduced to monitor the strength gain of structural adhesives. In this study, the curing process of the commercially available structural adhesive, Sikadur 330, was monitored using the EMI technique. Throughout the experimental study, the 7-day strength gain of the adhesive was observed from the movement of acquired frequency peaks. The frequency peaks moved noticeably to the right for the first 24 hours. After that, the rate of movement decreased significantly. An empirical equation is established to correlate the tensile strength of the adhesive to the acquired resonance frequency for different curing durations. The current study shows the capability of the EMI technique to monitor the strength gain of structural adhesives, particularly at an early age of curing

Monitoring the curing process of structural adhesives using the electromechanical impedance technique: A numerical investigation

Structural adhesives act as a bonding agent to externally bond fibre-reinforced polymer (FRP) composites onto existing structures for strengthening purposes. The performance of FRP-strengthened systems are therefore affected by the strength and stiffness of the structural adhesive layer. The lead zirconate titanate (PZT)-based electromechanical impedance (EMI) technique was employed in this study to monitor the stiffness development process of structural adhesives. A finite element model was developed to investigate the interaction between the PZT patches and the structural adhesive throughout the curing process. The dynamic elastic modulus of the structural adhesives can be predicted from the simulated EMI signatures. The EMI signatures were compared with experimental results for verification purposes. An empirical equation was established to predict the elastic modulus of structural adhesives from the resonance frequency. The current study can be extended by developing a model that predicts the tensile strength of structural adhesives at different curing durations

Pontecorvo's Original Oscillations Revisited

We show that a left-handed neutrino $\nu_L$ can oscillate into its $CP$- conjugated state $\bar{\nu}_R$ with maximal amplitude, in direct analogy with $K^0-\bar{K}^0$ oscillations. Peculiarities of such oscillations under different conditions are studied.Comment: LaTeX, 14 pages, 1 figure (not included but available upon request by fax or ordinary mail), SISSA 9/93/EP, IC/93/1

Minimal Mass Matrices for Dirac Neutrinos

We consider the possibility of neutrinos being Dirac particles and study minimal mass matrices with as much zero entries as possible. We find that up to 5 zero entries are allowed. Those matrices predict one vanishing mass state, CP conservation and U_{e3} either zero or proportional to R, where R is the ratio of the solar and atmospheric \Delta m^2. Matrices containing 4 zeros can be classified in categories predicting U_{e3} = 0, U_{e3} \neq 0 but no CP violation or |U_{e3}| \neq 0 and possible CP violation. Some cases allow to set constraints on the neutrino masses. The characteristic value of U_{e3} capable of distinguishing some of the cases with non-trivial phenomenological consequences is about R/2 \sin 2 \theta_{12}. Matrices containing 3 and less zero entries imply (with a few exceptions) no correlation for the observables. We outline models leading to the textures based on the Froggatt-Nielsen mechanism or the non-Abelian discrete symmetry D_4 \times Z_2.Comment: 32 pages, 3 figures. Comments and references added. To appear in JHE

Describing Analytically the Matter-Enhanced Two-Neutrino Transitions in a Medium

A general exact analytic expression for the probability of matter-enhanced two-neutrino transitions in a medium (MSW, RSFP, generated by neutrino FCNC interactions, etc.) is derived. The probability is expressed in terms of three real functions of the parameters of the transitions: the ``jump'' probability and two phases (angles). The results obtained can be utilized, in particular, in the studies of the matter-enhanced transitions/conversions of solar and supernova neutrinos. An interesting similarity between the Schroedinger equation for the radial part of the non-relativistic wave function of the hydrogen atom and the equation governing the MSW transitions of solar neutrinos in the exponentially varying matter density in the Sun is also briefly discussed.Comment: 14 pages, latex; published in Phys. Lett. B406 (1997) 35

Implications of Gallium Solar Neutrino Data for the Resonant Spin-Flavor Precession Scenario

We consider the implications of the recent results of SAGE and GALLEX experiments for the solution of the solar neutrino problem in the framework of the resonant neutrino spin-flavor precession scenario. It is shown that this scenario is consistent with all the existing solar neutrino data including the gallium results. The quality of the fit of the data depends crucially on the magnetic field profile used which makes it possible to get information about the magnetic field in the solar interior. In particular, the magnetic field in the core of the sun must not be too strong ($<3 \times 10^6$ G). The detection rate in the gallium detectors turns out to be especially sensitive to the magnitude of $\Delta m^2$. Predictions for forthcoming solar-neutrino experiments are made.Comment: LaTeX, 16 pages, 5 figures (not included by available upon request by fax or ordinary mail

Testing Matter Effects in Very Long Baseline Neutrino Oscillation Experiments

Assuming three-neutrino mixing, we study the capabilities of very long baseline neutrino oscillation experiments to verify and test the MSW effect and to measure the lepton mixing angle theta_13. We suppose that intense neutrino and antineutrino beams will become available in so-called neutrino factories. We find that the most promising and statistically significant results can be obtained by studying nu_e ->nu_mu and \bar{nu}_e-> \bar{nu}_mu oscillations which lead to matter enhancements and suppressions of wrong sign muon rates. We show the theta_13 ranges where matter effects could be observed as a function of the baseline. We discuss the scaling laws of rates, significances and sensitivities with the relevant mixing angles and experimental parameters. Our analysis includes fluxes, event rates and statistical aspects so that the conclusions should be useful for the planning of experimental setups. We discuss the subleading Delta m^2_{21} effects in the case of the LMA MSW solution of the solar problem, showing that they are small for L >= 7000 km. For shorter baselines, Delta m^2_{21} effects can be relevant and their dependence on L offers a further handle for the determination of the CP-violation phase \delta. Finally we comment on the possibility to measure the specific distortion of the energy spectrum due to the MSW effect.Comment: 30 pages, 13 figures, figures and more discussion added, results and conclusions unchange

On the Measurement of Solar Neutrino Oscillation Parameters with KamLAND

A new reactor power plant Shika-2, with a power of approximately 4 GW and at a distance of about 88 km from the KamLAND detector is scheduled to start operating in March 2006. We study the impact of the $\bar\nu_e$ flux from this reactor on the sensitivity of the KamLAND experiment to the solar neutrino oscillation parameters. We present results on prospective determination of $\Delta m^2_\odot$ and $\sin^2\theta_\odot$ using the combined data from KamLAND and the solar neutrino experiments, including the effect of the Shika-2 contribution to the KamLAND signal and the latest data from the salt enriched phase of the SNO experiment. We find that contrary to the expectations, the addition of the Shika-2 reactor flux does not improve the $\sin^2\theta_\odot$ sensitivity of KamLAND, while the ambiguity in $\Delta m^2_\odot$ measurement may even increase, as a result of the averaging effect between Kashiwazaki and the Shika-2 reactor contributions to the KamLAND signal.Comment: Version to appear in Phys. Lett.