No description available.

No description available.

The objective of this thesis was to assess the validity of the fluid-structure interaction (FSI) facilities in LS-DYNA for the analysis of highly deformable structures interacting with flowing viscous fluids. The collapsible tube experiment was chosen as a validation tool for FSI since its three-dimensional computational modelling would have been impossible if the viscous internal fluid flow were not considered. An explicit three-dimensional finite element model of a collapsible-tube was constructed and solved using LS-DYNA. The fully coupled model included internal fluid flow; external, inlet and outlet pressures; tube wall tension; pre-stressing; and contact. The finite element boundary conditions were taken as the recorded values of flow rate and pressure from a standard collapsible-tube experiment for both steady and unsteady flows. The predicted tube geometry in the steady LS-DYNA model showed good agreement with the experiment for operating points in the highly compliant region of the pressure-flow characteristic curve. The comparative position of the pinch at the outlet end differed by only 5.6% of the outlet diameter in the worst case. This analysis represents an advance on other published work in that previously no comparison with experiments have been drawn for FSI models involving high Reynolds number flowing viscous fluids interacting with highly deformable three dimensional structures. This analysis successfully made that comparison and the experimental and computational results have combined to form a more detailed picture of the collapsible-tube phenomenon by including detailed stress results of the tube walls and views of the internal fluid flow. The collapsible tube model exhibited uncertainty errors due to the use of a coarser than desirable mesh and a reduced fluid speed of sound. Although both these approximations caused significant error in the model both were necessary in order to achieve acceptable solution times. Because of these errors a thorough quantitative validation could not be achieved although LS-DYNA has been proven to be qualitatively accurate. Increases in computing speed are required before thorough quantitative validation of FSI can be achieved by comparison with the collapsible tube experiments.

Understanding PGE geochemistry in low abundance (i.e. sub ppb level) geological samples has been hampered by the absence of an accurate, low blank, preconcentration technique. Ni- S fire assay, the traditional preconcentration method, has been critically assessed and combined with isotope dilution to enable reproducible analysis of standards in the 1-l0ppb concentration range. In addition, a new anion exchange chromatography, low blank, isotope dilution method has been developed that allows analysis of Re, Os, Ir, Ru, Ft and Pd, at pg levels, from the same sample aliquot by ICP-MS. This method enables PGE abundances and Os isotopic ratios to be determined on the same sample dissolution, permitting geochronological studies. Samples are digested in Carius tubes and total procedural blanks are routinely less than l0pg/g for all elements, except Pt (25pg/g). Reproducibility is sufficient at the lOppt level to confidently identify inter-element PGE fractionations. Using this anion exchange preconcentration technique, PGEs have been characterised in a suite of plume-generated picrites from West Greenland, and a suite of subduction-related lavas, including fractionation series from Grenada (Lesser Antilles arc) and from Izu-Bonin. PGE concentrations are higher within the picrites of West Greenland, than in the picrites of Grenada, or boninites of Izu-Bonin. This is attributed to higher degrees of melting and less fractionation during West Greenland magma genesis. There is similarity in the PGE-pattems between all environments suggesting that relative PGE behaviour is not greatly altered during mantle melting in a subduction zone vs a plume. Subtle differences occur in inter-PGE ratios between the different environments and within the fractionation suites. Os and Ir do not behave in an analogous manner during fractionation indicating "compatibility" with different crystallising phases. The PGEs are associated with olivine fractionation in all of the primitive rock types, but, may also be compatible with other phases (e.g. magnetite/chromite/amphibole) during high-level fractionation in arc magma chambers. The PGE signatures in the evolved arc rocks are controlled by multi-stage fractionation. PGE concentrations decrease as fractionation progresses, except for Re and Ru. PGE compatibility during arc-lava fractionation decreases in the order Os>Ir>Pt>Pd>Ru>Re. There is not a strong sulfide control on PGE fractionation in any of the rock suites analysed, probably because the primary melts were generally S- undersaturated. This places important constraints on the nature of the mantle in the different tectonic environments. Os-isotopic studies indicate the presence of a radiogenic component in both the West Greenland picrite plume source region (recycled crust or outer core material) and the Grenada picrite source region (slab-derived fluids).

Abstract The degree of homogeneity and H-bond interaction in blends of low-molecular-mass poly(ethylene glycols) (PEG, Mw = 400, 600, 1000) and poly(vinylpyrrolidone) (PVP, Mw =9×103) prepared in supercritical CO2, ethanol and as physical mixtures were studied by differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy and dynamic mechanical analysis (DMA) techniques. Homogeneity of samples prepared in supercritical CO2 were greater than physically mixed samples, but slightly less than ethanol-cast samples. PEG–PVP H-bond interaction was higher for ethanol-cast blends when compared to blends prepared in supercritical CO2. This reduced interaction was attributed to a combination of: (1) shielding of PEG–PVP H-bond interactions when CO2 is dissolved in the blend; (2) rapidly reduced PEG and PVP chain mobility upon CO2 venting, delaying rearrangement for optimum PEG–PVP H-bond interaction.

No description available.

The motion of an incompressible fluid caused by the oscillation of a plane at plate of in nite length is termed Stokes' second problem. We assume zero velocity normal to the plate and thus simpli ed Navier-Stokes equations. For the unsteady Stokes' second problem, solutions may be obtained by using Laplace transforms, perturbation techniques, homotopy, di erential transform method or Adomian decomposition method. Stokes' second problem is discussed for second-grade and Oldroyd-B non-Newtonian fluids. This dissertation summarizes previously published work.

Lo Chi-keung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 69-72). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- What is an electrorheological fluid? --- p.1 / Chapter 1.2 --- Overview of recent theoretical studies on ER fluids --- p.2 / Chapter 1.3 --- Objectives of the thesis --- p.4 / Chapter 2 --- Review of some established macroscopic concepts --- p.8 / Chapter 2.1 --- Local field and depolarization tensor --- p.8 / Chapter 2.2 --- Clausius-Mossotti equation --- p.10 / Chapter 3 --- Ewald-Kornfeld formulation and effects of geometric anisotropy on local field distribution --- p.12 / Chapter 3.1 --- The development of the Ewald-Kornfeld method --- p.12 / Chapter 3.2 --- General Ewald-Kornfeld Formalism - point dipole approximation --- p.13 / Chapter 3.3 --- Ewald-Kornfeld Formalism - tetragonal lattice of point dipoles --- p.14 / Chapter 3.4 --- Numerical Results --- p.16 / Chapter 3.5 --- Contact with macroscopic concepts --- p.18 / Chapter 3.5.1 --- Generalized Clausius-Mossotti equation --- p.18 / Chapter 3.5.2 --- Onsager reaction field --- p.19 / Chapter 3.6 --- Figures --- p.22 / Chapter 4 --- Field-induced structure transformation in ER solid --- p.24 / Chapter 4.1 --- Ewald-Kornfeld Formalism - body-centered tetragonal lattice --- p.25 / Chapter 4.2 --- Effects of structure transformation on the local field --- p.27 / Chapter 4.3 --- Structure transformation via rotating electric fields --- p.28 / Chapter 4.4 --- Competitions between FCC and HCP --- p.30 / Chapter 4.5 --- Figures --- p.31 / Chapter 5 --- Geometric anisotropy from distortive lattices: ferrodistortive and antidistortive systems --- p.34 / Chapter 5.1 --- Ferrodistortive lattice --- p.35 / Chapter 5.1.1 --- Sublattice interaction tensors --- p.36 / Chapter 5.1.2 --- Effective polarizability and Clausius-Mossotti equation --- p.37 / Chapter 5.2 --- Antidistortive lattice --- p.39 / Chapter 5.2.1 --- Sublattice interaction tensors --- p.40 / Chapter 5.2.2 --- Sublattice dipole moments --- p.41 / Chapter 5.2.3 --- Effective polarizability and polarization catastrophe --- p.43 / Chapter 5.2.4 --- Depolarization field --- p.44 / Chapter 5.3 --- Experimental realization - colloidal self-assembly --- p.45 / Chapter 5.4 --- Figures --- p.46 / Chapter 6 --- Discussion and conclusion --- p.52 / Chapter 6.1 --- Discussion on our work and possible future extension --- p.52 / Chapter 6.2 --- Conclusion --- p.54 / Chapter A --- Piezoelectric coefficients by Ewald-Kornfeld formulation --- p.57 / Chapter B --- Alternative formulation for Ewald-Kornfeld formulation by di- rect calculations of the dipole interaction tensor --- p.59 / Chapter C --- Ewald-multipole formulation --- p.63 / Chapter C.1 --- Multipole fields --- p.64 / Chapter C.2 --- Coupled dipole-quadrupole lattice --- p.66 / Bibliography --- p.69

Shen Lei = 旋转颗粒的动态电流变效应 / 沈雷. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 68-72). / Text in English; abstracts in English and Chinese. / Shen Lei = Xuan zhuan ke li de dong tai dian liu bian xiao ying / Shen Lei. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- ER fluids and dynamic ER effects --- p.1 / Chapter 1.2 --- Negative ER effects and Quincke Rotations --- p.3 / Chapter 1.3 --- Recent works on ER fluids --- p.5 / Chapter 1.4 --- Objectives of the thesis --- p.8 / Chapter 2 --- Dynamic ER effects of two-body systems --- p.10 / Chapter 2.1 --- Formalism under the point-dipole approximation --- p.10 / Chapter 2.2 --- Numerical results under the point-dipole approximation --- p.20 / Chapter 2.3 --- Discussions under the MID approximation --- p.25 / Chapter 2.4 --- Conclusion --- p.28 / Chapter 3 --- Dynamic ER effects of periodic boundary systems --- p.30 / Chapter 3.1 --- Ewald-Kornfeld formulation --- p.31 / Chapter 3.2 --- Structure transformation in ER solids induced by particle rota- tions --- p.36 / Chapter 3.3 --- Structure transformation in ER solids induced by field rotations --- p.42 / Chapter 3.4 --- Discussion and conclusion --- p.45 / Chapter 4 --- Dynamic ER effects of Quincke rotations --- p.48 / Chapter 4.1 --- Formalism --- p.49 / Chapter 4.2 --- Molecular dynamics simulations --- p.51 / Chapter 4.3 --- Numerical results --- p.54 / Chapter 4.4 --- Self assembly of Quincke rotors --- p.61 / Chapter 4.5 --- Discussion and conclusion --- p.62 / Chapter 5 --- Summary --- p.65 / Bibliography --- p.68 / Chapter A --- Derivation of the multiple image expression --- p.73 / Chapter A.1 --- Images of a point charge --- p.73 / Chapter A.2 --- Images of a point dipole --- p.74 / Chapter A.3 --- Images of a pair of spheres --- p.76 / Chapter B --- Optimizations of the Ewald summation --- p.81

磁流變阻尼器可用於各種動態系統的半主動振動控制，非常有前景。在當前的磁流變阻尼器系統中，需要使用外加并分離的電源和動態傳感器。本論文提出并探索了自供能自傳感磁流變阻尼器。它將能源採集、動態傳感和磁流變阻尼三種技術集成到同一器件中，具有內置的發電機制，和速度/位移傳感能力。此多功能的集成可以對當前的磁流變阻尼器系統帶來眾多的益處，如更節能、更高的可靠性、尺寸及重量的減少、較低的成本、以及更少的維護需求。該研究成果可以促進各種動態系統，如懸架系統和義肢的發展。 / 在論文中，作者對自供能自傳感磁流變阻尼器的概念、原理、設計方法、設計難點及解決方案進行了探討，設計製作了兩件原型，並對原型進行了性能測試。作者提出并探索了幾種可與磁流變阻尼器集成的發電機制，和動態傳感的方法。對發電、動態傳感和阻尼力三種性能，進行了建模、理論分析、以及實驗驗證。作者提出并驗證了自供能自傳感磁流變阻尼器的數學模型，該模型考慮了單獨的功能以及多功能間的相互作用。本論文對自供能磁流變阻尼器系統進行了探討分析，包括能源產生與磁流變阻尼的相互作用、自供能判據、工作範圍和設計指引。還提出并探索了一個自供能控制器，以及一種複合的磁場隔離方法。 / Magnetorheological (MR) dampers are promising for semi-active vibration control of various dynamic systems. In the current MR damper system, separate power supply and dynamic sensor are required. This research is aimed to propose and investigate self-powered, self-sensing (SPSS) MR dampers, which integrate energy harvesting, sensing and MR damping technologies into one device. SPSS MR damper has self-contained power generation and velocity/displacement sensing capabilities. This multifunctional integration will bring great benefits such as energy saving, higher reliability, size and weight reduction, lower cost, and less maintenance for the use of MR damper systems. It will advance the technology of various dynamic systems such as suspensions and prostheses. / Concepts, principles, design methodology, key issues and solutions of SPSS MR dampers are studied. Two prototypes of the SPSS MR dampers are designed, fabricated, and tested. Several integrated power generation and sensing methods for MR dampers are proposed and investigated. Modeling, theoretical analyses, and experimental studies on power generation ability, sensing capability and damping force performances are conducted. Models of SPSS MR dampers considering individual functions and interactions are developed and validated experimentally. Systematic studies on the self-powered MR damper system are performed, including interaction between the power generation and MR damping, self-powered criterion, working range and design guidelines. Moreover, a self-powered controller and combined magnetic-field isolation method are proposed and investigated. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chen, Chao. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 163-172). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / ABSTRACT --- p.i / 摘要 --- p.iii / TABLE OF CONTENTS --- p.vii / LIST OF FIGURES --- p.xi / LIST OF TABLES --- p.xvii / Chapter 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background and Motivation --- p.2 / Chapter 1.1.1 --- MR fluids --- p.2 / Chapter 1.1.2 --- MR dampers --- p.3 / Chapter 1.1.3 --- Previous research on functional integration of MR dampers --- p.7 / Chapter 1.2 --- Research Objective --- p.10 / Chapter 1.3 --- Thesis Organization --- p.12 / Chapter 2 --- DESIGN OF SELF-POWERED, SELF-SENSING MR DAMPERS --- p.13 / Chapter 2.1 --- Concept and Key Issues of Multifunctional Integration --- p.14 / Chapter 2.2 --- Configurations of Different Methods of Multiple Functions --- p.17 / Chapter 2.3 --- Principles of SPSS MR Dampers --- p.18 / Chapter 2.3.1 --- Structure and operation principle of the first prototype --- p.18 / Chapter 2.3.2 --- Structure and operation principle of the second prototype --- p.21 / Chapter 2.3.3 --- Energy flow of SPSS MR damper --- p.25 / Chapter 2.4 --- Materials Used in Design --- p.27 / Chapter 2.5 --- Fabrication of Prototypes --- p.32 / Chapter 2.6 --- Experimental Setup --- p.35 / Chapter 2.7 --- Chapter Summary --- p.37 / Chapter 3 --- POWER GENERATION OF SELF-POWERED, SELF-SENSING MR DAMPERS --- p.39 / Chapter 3.1 --- Introduction to Electromagnetic Energy Harvesting --- p.40 / Chapter 3.2 --- Finite Element Method --- p.42 / Chapter 3.3 --- Slotted Power Generation Method --- p.44 / Chapter 3.3.1 --- Modeling and analysis of slotted power generation --- p.44 / Chapter 3.3.2 --- Experimental results of slotted power generation --- p.52 / Chapter 3.4 --- Slotless Power Generation Method --- p.56 / Chapter 3.4.1 --- Design considerations --- p.56 / Chapter 3.4.2 --- Modeling and analysis of slotless power generation --- p.57 / Chapter 3.4.3 --- Experimental results of slotless power generation --- p.62 / Chapter 3.5 --- Frequency Multiplication Effect of Generated Voltage --- p.65 / Chapter 3.6 --- Chapter Summary --- p.67 / Chapter 4 --- SENSING OF SELF-POWERED, SELF-SENSING MR DAMPERS --- p.69 / Chapter 4.1 --- Introduction to Self-sensing Ability --- p.70 / Chapter 4.1.1 --- Self-sensing for vibration control --- p.70 / Chapter 4.1.2 --- Self-sensing of SPSS MR damper --- p.71 / Chapter 4.2 --- Moving-spacer Velocity Sensing Method --- p.73 / Chapter 4.3 --- Velocity-extraction Method from Slotted Power Generator --- p.80 / Chapter 4.4 --- Velocity-extraction Method from Slotless Power Generator --- p.86 / Chapter 4.5 --- Chapter Summary --- p.90 / Chapter 5 --- DAMPING FORCE OF SELF-POWERED, SELF-SENSING MR DAMPERS --- p.93 / Chapter 5.1 --- Design of MR Damping Part --- p.94 / Chapter 5.2 --- Testing Results of MR Damping Force of the First Prototype --- p.97 / Chapter 5.3 --- Testing Results of Damping Force of the Improved Prototype --- p.101 / Chapter 5.4 --- Damping Force Modeling and Identification --- p.105 / Chapter 5.5 --- Chapter Summary --- p.110 / Chapter 6 --- INTERACTION ANALYSIS --- p.111 / Chapter 6.1 --- Modeling Summary and Magnetic Field Interactions of SPSS MRD --- p.112 / Chapter 6.1.1 --- Modeling summary of SPSS MR dampers --- p.112 / Chapter 6.1.2 --- Magnetic field interactions --- p.114 / Chapter 6.2 --- Analysis of a Versatile Self-powered MR Damper System --- p.122 / Chapter 6.3 --- Application to Vehicle Suspension Systems --- p.130 / Chapter 6.3.1 --- Modeling of suspension system --- p.131 / Chapter 6.3.2 --- Working range and vibration control efficiency under on-off controller --- p.133 / Chapter 6.4 --- Design Guidelines of Self-powered Working Range --- p.141 / Chapter 6.5 --- A Proposed Self-powered Controller --- p.146 / Chapter 6.6 --- Chapter Summary --- p.153 / Chapter 7 --- CONCLUSION AND FUTURE WORK --- p.155 / Chapter 7.1 --- Conclusion --- p.155 / Chapter 7.2 --- Future Work --- p.160 / Chapter 8 --- BIBLIOGRAPHY --- p.163 / Chapter 9 --- APPENDIX --- p.173 / Chapter A. --- MR Fluid Datasheet --- p.173 / Chapter B. --- Sectional Views of Prototypes --- p.175