Todd S. Coffey

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Pseudo-transient continuation is a practical technique for globalizing the computation of steady-state solutions of nonlinear differential equations. The technique employs adaptive time-stepping to integrate an initial value problem derived from an underlying ODE or PDE boundary value problem until sufficient accuracy in the desired steady-state root is(More)
In this paper, we explore in detail the stability properties of time-domain numerical methods for multi-time partial differential equations (MPDEs). We demonstrate that simple techniques for numerical discretization can lead easily to instability. By investigating the underlying eigenstructure of several discretization techniques along different artificial(More)
We consider the simulation of steady-state variably saturated groundwater flow using Richards' equation (RE). The difficulties associated with solving RE numerically are well known. Most discretization approaches for RE lead to nonlinear systems that are large and difficult to solve. The solution of nonlinear systems for steady-state problems can be(More)
The ability to automatically morph an existing mesh to conform to geometry modifications is a necessary capability to enable rapid prototyping of design variations. This paper compares six methods for morphing hexahe-dral and tetrahedral meshes, including the previously published FEMWARP and LBWARP methods as well as four new methods. Element quality and(More)
Protein therapeutics have unique critical quality attributes (CQAs) that define their purity, potency, and safety. The analytical methods used to assess CQAs must be able to distinguish clinically meaningful differences in comparator products, and the most important CQAs should be evaluated with the most statistical rigor. High-risk CQA measurements assess(More)
Traditional factorial designs for evaluating interactions among chemicals in a mixture may be prohibitive when the number of chemicals is large. Using a mixture of chemicals with a fixed ratio (mixture ray) results in an economical design that allows estimation of additivity or nonadditive interaction for a mixture of interest. This methodology is extended(More)
For biosimilar drug development, it is critical to demonstrate similar physiochemical characteristics, efficacy, and safety of the biosimilar product compared to the reference product. Therefore, pharmacokinetic (PK) and immunogenicity (antidrug antibody, ADA) assays that allow for the demonstration of biosimilarity are critical. Under the auspices of the(More)
Multiple types of outcomes are sometimes measured on each animal in toxicology dose-response experiments. The potential false-positive rate from statistical tests on each endpoint may be inflated. We introduce a method of deriving a composite score that combines information from discrete and continuous outcomes through the use of desirability functions.(More)
Experienced PhD biostatistician with demonstrated leadership in implementing statistical thinking throughout the process sciences, quality, bioanalytical, in vivo/pharmacology, and translational medicine groups. Proficient in statistical approaches for combination drug discovery, design of experiments (DOE), statistical process control (SPC), and the(More)
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