As part of the ONR sponsored Coupled Boundary Layer/Air-Sea Transfer (CBLAST) experiment, data from the NOAA WP-3D research aircraft measurements into major Hurricanes in the 2002-2004 seasons are analyzed to investigate the structure of the boundary layer. The turbulent fluxes of momentum and enthalpy are derived using the eddy correlation method. For the first time, the momentum and enthalpy fluxes were directly measured in the boundary layer of a hurricane with wind speeds up to 30 m/s. A new bulk parameterization of the momentum and enthalpy flux is developed. The vertical structure of turbulence and fluxes are presented for the entire boundary layer in the rain free region between the outer rainbands. The turbulent kinetic energy budget was estimated for the hurricane boundary layer between the outer rainbands. The universal spectra and cospectra of the wind velocity, temperature and humidity are also derived. A case study on the effects of roll vortices on the turbulent fluxes is conducted, which confirmed the existence of the boundary layer rolls and gave the first estimate of their modulation of the momentum and sensible heat flux. The CBLAST data provided an invaluable perspective on the evaluation and development of the boundary layer parameterization suited for the hurricane models. Studies on entrainment processes above of the mixed layer and turbulent transport processes induced by the inflow are recommended in the future.

Motivated by recent research to automate radiotherapy, this thesis looks into feedback control problems where the feedback sensor imposes considerable time delay. The use of an asymptotic estimator is considered as a method to compensate for the time delay. Properties and parameterizations of asymptotic estimators are analyzed. It is shown that if such a delay compensation scheme is adopted, a separation principle holds, which allows for independent design of the feedback controller and the time delay compensator. The radiotherapy problem is used as a case study to show how asymptotic estimators may be designed, exploiting the separation principle. Lastly, the thesis considers multivariable versions of asymptotic estimators.

Motivated by recent research to automate radiotherapy, this thesis looks into feedback control problems where the feedback sensor imposes considerable time delay. The use of an asymptotic estimator is considered as a method to compensate for the time delay. Properties and parameterizations of asymptotic estimators are analyzed. It is shown that if such a delay compensation scheme is adopted, a separation principle holds, which allows for independent design of the feedback controller and the time delay compensator. The radiotherapy problem is used as a case study to show how asymptotic estimators may be designed, exploiting the separation principle. Lastly, the thesis considers multivariable versions of asymptotic estimators.

Global climate models (GCM) have been used for nearly two decades now as a tool to investigate and analyze past, present, and future weather and climate. Even though the first several generations of climate models were very simple, today's models are very sophisticated. They use complex parameterization schemes to approximate many nonlinear physical fields. In these models, the resolution and time steps can be set to be as small or as large as desired. In either case, the model generates over 100 atmospheric variables and 20 land surface variables that can be reported daily or monthly. The Community Atmospheric Model Version Two global climate model spends over sixty percent of the time computing shortwave and longwave parameterization schemes. Our goal is to replace its shortwave scheme with empirical methods and show that accuracy of the tropospheric variables is not compromised when using these empirical methods. We found that an autoregressive moving average (ARMA) model can be used to simulate the solar radiation at the top of the model atmosphere. However, the calculated insolation value is only valid for one particular grid point. To simulate the radiation over the entire globe, many ARMA models need to be determined. We also found that large 4-10-10-1 neural networks can be used to simulate the solar radiation to within 2 W m-2. However, much smaller and manageable neural networks can be used to simulate the complete solar insolation term if the neural network only simulates the residual after the annual and diurnal cycles and removed from the field (referred to as the - method). By using the neural network in the - method and by setting the eccentricity term to a constant, we were able to cut the models processing of the solar insolation by at least a factor of four.

Stability is a critical issue in gain-scheduled control problems in that the closed loop system may not be stable during the transitions between operating conditions despite guarantees that the gain-scheduled controller stabilizes the plant model at fixed values of the scheduling variable. For Linear Parameter Varying (LPV) model representations, a controller interpolation method using Youla parameterization that guarantees stability despite fast transitions in scheduling variables is proposed. By interconnecting an LPV plant model with a Local Controller Network (LCN), the proposed Youla parameterization based controller interpolation method allows the interpolation of controllers of different size and structure, and guarantees stability at fixed points over the entire operating region. Moreover, quadratic stability despite fast scheduling is also guaranteed by construction of a common Lyapunov function, while the characteristics of individual controllers designed a priori at fixed operating condition are recovered at the design points. The efficacy of the proposed approach is verified with both an illustrative simulation case study on variation of a classical MIMO control problem and an experimental implementation on a multi-evaporator vapor compression cycle system. The dynamics of vapor compression systems are highly nonlinear, thus the gain-scheduled control is the potential to achieve the desired stability and performance of the system. The proposed controller interpolation/switching method guarantees the nonlinear stability of the closed loop system during the arbitrarily fast transition and achieves the desired performance to subsequently improve thermal efficiency of the vapor compression system.

The intra-continental movement of waterborne contaminants is governed by the distribution of solute load in the landscape along with the characteristics and distribution of the hydrological pathways that transport the solutes. An understanding of the processes affecting the transport and fate of the contaminants is crucial for assessments of solute concentrations and their environmental effect on downstream recipients. Elevated concentration of nutrients and the presence of anthropogenic substances, such as pharmaceutical residues, are two examples of the current problems related to hydrological transport. The overall objective of this thesis is to increase the mechanistic understanding of the governing hydrological transport processes and their links to geomorphological and biogeochemical retention and attenuation processes. Specifically, this study aims to quantify the processes governing the transport and fate of waterborne contaminants on the point, stream reach, and watershed scales by evaluating time series obtained from stream tracer tests and water quality monitoring data. The process quantification was achieved by deriving formal expressions for the key transport characteristics, such as the central temporal moments of a unit solute response function and the spectral scaling function for time series of solute responses, which attributes the solute response in the Laplace and Fourier domains to the governing processes and spatial regions within the watershed. The results demonstrate that in addition to the hydrological and biogeochemical processes, the distribution of the load in the landscape and the geomorphological properties in terms of the distribution of transport pathway distances have defined effects on the solute response. Furthermore, the spatial variability between and along the transport pathways significantly affect the solute response. The results indicate that environments with high retention and attenuation intensity, such as stream-reaches with pronounced hyporheic zones, may often dominate the solute flux in the watershed effluent, especially for reactive solutes. The mechanistic-based framework along with the evaluation methodologies presented within this study describes how the results can be generalized in terms of model parameters that reflect the hydrology, geomorphology and biogeochemistry in the studied area. This procedure is demonstrated by the parameterization of a compartment-in-series model for phosphorous transport. / <p>QC 20140826</p>

With continually growing availability of high performance computing resources, the finite element methods (FEM) are becoming increasingly more efficient and practical research tools. In the domain of computational biomechanics, FEMs have been successfully applied in investigation of biomedical problems that include impact and fracture mechanics of bone, load transmission through the joints, feasibility of joint replacements, and many others. The present research study was concerned with the development of a detailed, anatomically accurate, finite element model of the human hand and wrist. As a first step in this direction, we used a publically available database of wrist bone anatomy and carpal kinematics to construct a multi-body statistical shape model (SSM) of the wrist. The resulting model provides an efficient parameterization of anatomical variations of the entire training set and can thus overcome the major shortcoming of conventional biomechanical models associated with limited generalization ability. The main contributions of this work are: 1) A robust method for constructing multi-body SSM of the wrist from surface meshes. 2) A novel technique for resampling closed genus-0 meshes to produce high quality triangulations suitable for finite element simulations. Additionally, all techniques developed in the course of this study could be directly applied to create an equivalent model of the tarsus.

This dissertation aims to study the broadband optical properties and radiative effects of dust aerosols and ice clouds. It covers three main topics: the uncertainty of dust optical properties and radiative effects from the dust particle shape and refractive index, the influence of ice particle surface roughening on the global cloud radiative effect, and the simulations of the global contrail radiative forcing. In the first part of this dissertation, the effects of dust non-spherical shape on radiative transfer simulations are investigated. We utilize a spectral database of the single-scattering properties of tri-axial ellipsoidal dust-like aerosols and determined a suitable dust shape model. The radiance and flux differences between the spherical and ellipsoidal models are quantified, and the non-spherical effect on the net flux and heating rate is obtained over the solar spectrum. The results indicate the particle shape effect is related to the dust optical depth and surface albedo. Under certain conditions, the dust particle shape effect contributes to 30% of the net flux at the top of the atmosphere. The second part discusses how the ice surface roughening can exert influence on the global cloud radiative effect. A new broadband parameterization for ice cloud bulk scattering properties is developed using severely roughened ice particles. The effect of ice particle surface roughness is derived through simulations with the Fu-Liou and RRTMG radiative transfer codes and the Community Atmospheric Model. The global averaged net cloud radiative effect due to surface roughness is around 1.46 Wm-2. Non-negligible increase in longwave cloud radiative effect is also found. The third part is about the simulation of global contrail radiative forcing and its sensitivity studies using both offline and online modeling frameworks. Global contrail distributions from the literature and Contrail Cirrus Prediction Tool are used. The 2006 global annual averaged contrail net radiative forcing from the offline model is estimated to be 11.3 mW m^(-2), with the regional contrail radiative forcing being more than ten times stronger. Sensitivity tests show that contrail effective size, contrail layer height, the model cloud overlap assumption, and contrail optical properties are among the most important factors.

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