Thesis (Ph.D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains ix, 176 p.; also includes graphics. Includes bibliographical references (p. 172-176). Available online via OhioLINK's ETD Center

This thesis is dedicated to the so-called Dirichlet-to-Neumann map associated with the weighted 𝑝-Laplace operator. In Chapter 1, we begin by deriving the Dirichlet-to-Neumann map by using classical modelling and outline why it is interesting to study this boundary operator. In the remaining part of Chapter 1, we dedicate each section an overview about the content of one chapter and summarize the main results. Chapter 2 is dedicated to the Poisson problem and the inverse of the Dirichlet-to-Neumann map. Chapter 3 provides the first main application of the Dirichlet-to-Neumann map, namely, it generates a strongly continuous semigroup of contractions on the Lebesgue space 𝐿2 and this contraction can be extrapolated to a contraction on 𝐿q for all 1 ≤ 𝑞 ≤ ∞. In Chapter 4, we develop an abstract theory to establish global 𝐿𝑞-𝐿∞ regularization estimates satisfied by the semigroup generated by the negative Dirichlet-to-Neumannmap. Chapter 5 is concerned with 𝐿1 and point-wise estimates on the time-derivative of the semigroup generated by the neagtive Dirichlet-to- Neumann map, which are known in the literatur as Aronson-Bénilan type estimates. In Chapter 6, we outline the theory of 𝑗-functional and its application to evolution problems. This theory allows us to study the Dirichlet problem on general open sets Ω, and to realize the Dirichlet-to-Neumann map as an operator in 𝐿2 (𝜕Ω). In Chapter 7, we consider the limit case 𝑝 = 1, which corresponds to the Dirichlet-to-Neumann map associated with the (unweighted) 1-Laplace operator. Each chapter covers parts of the authors papers mentioned in the references.:Chapter 1 Introduction................................................... 1 1.1 Motivation-physical background ............................. 2 1.2 The Dirichlet-to-Neumann map - an analyst’s perspective . . . . . . . . . 5 1.2.1 Step1. The Dirichlet problem.......................... 5 1.2.2 Step2. The Neumann boundary operator ................ 8 2 1.3 The Dirichlet-to-Neumann map on 𝐿2 ......................... 9 1.4 The Dirichlet-to-Neumann map and Leray-Lions operators . . . . . . . . 11 1.5 The Dirichlet-to-Neumann map is a nonlocal operator . . . . . . . . . . . . 12 1.6 The Dirichlet-to-Neumann map on open sets.................... 13 1.6.1 𝑗-elliptic functionals and their 𝑗-subgradient . . . . . . . . . . . . . 13 1.6.2 The construction of a weak trace on open sets ............ 15 1.6.3 Construction of the Dirichlet-to-Neumann map . . . . . . . . . . . 17 1.7 The Poisson problem and the Neumann-to-Dirichlet map . . . . . . . . . 19 1.8 Evolution problems governed by the Dirichlet-to-Neumann map . . . 21 1.9 𝐿𝑞-𝐿∞ regularization and decay estimates...................... 27 1.10 Aronson-Bénilantypeestimates .............................. 30 1.11 The Dirichlet-to-Neumann map associated with the 1-Laplacian . . . 33 Chapter 2 The Poisson problem and the Neumann-to-Dirichlet map . . . . . . . . . . . 45 2.1 The Poisson problem........................................ 45 2.2 Preliminaries .............................................. 46 2.3 The Dirichlet problem....................................... 48 2.4 The Dirichlet-to-Neumann map............................... 51 2.5 Proof of Theorem 2.1 ....................................... 56 2.5.1 Proof of claim (1) of Theorem 2.1 ...................... 56 2.5.2 Preliminaries for the proof of claim (2) of Theorem 2.1 . . . . 58 2.5.3 Proof of claim( 2) of Theorem 2.1 ...................... 60 Chapter 3 Nonlinear elliptic-parabolic evolution problems.................... 61 3.1 Main result................................................ 61 3.2 Preliminaries .............................................. 64 3.2.1 Some function spaces................................. 64 3.2.2 Nonlinear semigroupt heory - Part I..................... 65 3.2.3 Homogeneous operators - Part I ........................ 75 2 3.3 The Dirichlet-to-Neumann map on 𝐿2 ...................... 77 3.4 The Dirichlet-to-Neumann map on 𝐿1, 𝐿𝜓 and C................ 82 3.5 Proof of Theorem 3.1 ....................................... 84 Chapter 4 𝑳𝒒-𝑳∞ regularization and decay estimates ........................ 89 4.1 Main results............................................... 89 4.2 Preliminaries .............................................. 91 4.3 Sobolev implies 𝐿𝑞 -𝐿𝑟 regularization estimates ................. 92 4.4 Extrapolation towards 𝐿1 .................................... 98 4.5 A nonlinear interpolation theorem.............................100 4.6 Extrapolation towards 𝐿∞ via interpolation of the semigroup . . . . . . 107 4.7 Proof of Theorem 4.1 .......................................115 Chapter 5 Aronson-Bénilan type estimates..................................117 5.1 Main results ...............................................117 5.2 Preliminaries ..............................................119 5.2.1 Nonlinearsemigrouptheory-PartII ....................119 5.2.2 Homogeneousaccretiveoperators ......................130 5.2.3 Homogeneous completely accretive operators . . . . . . . . . . . . 138 5.3 Proof of Theorem 5.1 .......................................141 Chapter 6 The Dirichlet-to-Neumann map on open sets ......................143 6.1 Main results ...............................................143 6.2 The 𝑗-subgradient and basic properties ........................146 6.2.1 Definition and characterisation as a classical gradient . . . . . . 146 6.2.2 Ellipticextensions ...................................151 H 6.2.3 Identification of 𝜑 ..................................152 6.2.4 The case when 𝑗 is a weakly closed operator .............155 6.3 Semigroups and invariance of convex sets ......................156 6.3.1 Positive semigroups ..................................160 6.3.2 Comparison and domination of semigroups ..............161 6.3.3 𝐿∞-contractivity and extrapolation of semigroups . . . . . . . . . 163 6.4 Application:The Dirichlet-to-Neumann map....................168 Chapter 7 The Dirichlet-to-Neumann map associated with the 1-Laplacian . . . . . 171 7.1 Preliminaries ..............................................171 7.1.1 Functions of bounded variation.........................171 7.1.2 Nonlinear semigroup theory - Part III ...................178 7.2 The Dirichlet problem for the 1-Laplace operator................180 7.3 A Robin-type problem for the 1-Laplace operator................187 7.4 Proofs of the main results....................................189 7.4.1 The Dirichlet-to-Neumann operator in 𝐿1 ................189 7.4.2 The Dirichlet-to-Neumann operator in 𝐿2 ................200 7.4.3 The Dirichlet-to-Neumann operator in 𝐿1 (continued)...........204 7.4.4 Long-timestability...................................206 Appendix A Weighted Sobolev Spaces........................................213 A.1 p-admissible weights........................................213 B Mean spaces by Lions and Peetre ................................215 B.1 The connection between mean spaces and 𝐿p spaces.............215 References . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 219 Index .............................................................227

Master of Science / Department of Mechanical Engineering / Warren N. White / The subject of linear control is a mature subject that has many proven powerful techniques. Recent research generally falls into the area of non-linear control. A subsection of non-linear control that has garnered a lot of research recently has been in underactuated dynamic systems. Many applications of the subject exist in robotics, aerospace, marine, constrained systems, walking systems, and non-holonomic systems. This thesis proposes a sliding mode control law for the tracking control of an underactuated dynamic system. A candidate Lyapunov function is used to build the desired tracking control. The proposed control method does not require the integration of feedback as does its predecessor. The proposed control can work on a variety of underactuated systems. Its predecessor only worked on those dynamic systems that are simply underactuated (torques acting on some joints, no torques acting on others). For dynamic systems that contain a roll without slip constraint, often a desired trajectory to follow is related to dynamic coordinates through a non-holonomic constraint. A navigational control is shown to work in conjunction with the sliding mode control to allow tracking of these desired trajectories. The methodology is applied through simulations to a holonomic case of the Segbot, an inverted cart-pole, a non-holonomic case of Segbot, and a rolling wheel. The methodology is implemented on an actual Segbot and shown to provide more favorable tracking results than linear feedback gains.

This dissertation begins with a study of some of the linear and nonlinear optical properties of composite materials consisting of CdSₓSe₁₋ₓ microcrystallites embedded in a host glass matrix. These studies investigate changes in absorption, refractive index and nonlinear response time under a variety of experimental conditions. The data demonstrates that this class of materials exhibit: a strong saturation of absorption due to band filling; a large n₂ which also saturates; response times which range from <100ps to many nanoseconds; and a permanent darkening and change of n₂ induced by extended exposure to high energy pulses. These measurements were used to identify the optimum sample of the semiconductor doped glasses to demonstrate an efficient degenerate four-wave mixing process within a planar waveguide. High quality single mode waveguides were fabricated from the semiconductor doped glass by K⁺-ion exchange. Four wave mixing was performed in the waveguide that produced a peak reflectivity of ≅.003, which is 8 orders of magnitude larger than that achieved previously in a similar experiment where CS₂ was used as the nonlinear medium.

The objective of this thesis is to develop a theoretical understanding of computation in networked dynamical systems and demonstrate practical applications supported by the theory. We are interested in understanding how networks of locally interacting agents can be controlled to compute arbitrary functions of the initial node states. In other words, can a dynamical networked system be made to behave like a computer? In this thesis, we take steps towards answering this question with a particular model class for distributed, networked systems which can be made to compute linear transformations.

This work is centered on the modeling, experimental identification, and dynamic interaction of inherently present and intentionally designed nonlinearities of piezoelectric structures focusing on applications to vibration energy harvesting. The following topics are explored in this theoretical and experimental research: (1) frequency bandwidth enhancement using a simple, intentionally designed, geometrically nonlinear M-shaped oscillator for low-intensity base accelerations; (2) multi-term harmonic balance analysis of this structure for primary and secondary resonance behaviors when coupled with piezoelectrics and an electrical load; (3) inherent electroelastic material softening and dissipative nonlinearities for various piezoelectric materials with a dynamical systems approach; and (4) development of a complete approximate analytical multiphysics electroelastic modeling framework accounting for material, dissipative, and strong circuit nonlinearities. The ramifications of this research extend beyond energy harvesting, since inherent nonlinearities of piezoelectric materials are pronounced in various applications including sensing, actuation, and vibration control, which can also benefit from bandwidth enhancement from designed nonlinearities.

No description available.

Longitudinal optical binding refers to the light induced self organisation of micro particles in one dimension. In this thesis I will present experimental and theoretical studies of the separation between two dielectric spheres in a counter-propagating (CP) geometry. I will explore the bistable nature of the bound sphere separation and its dependency on the refractive index mismatch between the spheres and the host medium, with an emphasis on the fibre separation. The physical under pining principle of longitudinal optical binding in the Mie regime is the refocusing effect of the light field from one sphere to its nearest neighbour. In a second set of experiments I developed means to visualise the field intensity distribution responsible for optical binding using two-photon fluorescence imaging from fluorescein added to the host medium. The experimental intensity distributions are compared to theoretical predictions and provide an in situ method to observe the binding process in real time. This coupling via the refocused light fields between the spheres is in detailed investigated experimentally and theoretically, in particular I present data and analysis on the correlated behaviour of the micro spheres in the presence of noise. The measurement of the decay times of the correlation functions of the modes of the optically bound array provides a methodology for determining the optical restoring forces acting in optical binding. Interestingly micro devices can be initiated by means of the light-matter interaction. Light induced forces and torques are exerted on such micro-objects that are then driven by the optical gradient or scattering force. I have experimentally investigate how the driving light interacts with and diffracts from the motor, utilising two-photon imaging. The micromotor rotation rate dependence on the light field parameters is explored and theoretically modelled. The results presented will show that the model can be used to optimise the system geometry and the micromotor.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy