616 research outputs found
Optimal and efficient crossover designs for comparing test treatments with a control treatment
This paper deals exclusively with crossover designs for the purpose of
comparing t test treatments with a control treatment when the number of periods
is no larger than t+1. Among other results it specifies sufficient conditions
for a crossover design to be simultaneously A-optimal and MV-optimal in a very
large and appealing class of crossover designs. It is expected that these
optimal designs are highly efficient in the entire class of crossover designs.
Some computationally useful tools are given and used to build assorted small
optimal and efficient crossover designs. The model robustness of these newly
discovered crossover designs is discussed.Comment: Published at http://dx.doi.org/10.1214/009053604000000887 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Efficient decoupling schemes with bounded controls based on Eulerian orthogonal arrays
The task of decoupling, i.e., removing unwanted interactions in a system
Hamiltonian and/or couplings with an environment (decoherence), plays an
important role in controlling quantum systems. There are many efficient
decoupling schemes based on combinatorial concepts like orthogonal arrays,
difference schemes and Hadamard matrices. So far these (combinatorial)
decoupling schemes have relied on the ability to effect sequences of
instantaneous, arbitrarily strong control Hamiltonians (bang-bang controls). To
overcome the shortcomings of bang-bang control Viola and Knill proposed a
method called Eulerian decoupling that allows the use of bounded-strength
controls for decoupling. However, their method was not directly designed to
take advantage of the composite structure of multipartite quantum systems. In
this paper we define a combinatorial structure called an Eulerian orthogonal
array. It merges the desirable properties of orthogonal arrays and Eulerian
cycles in Cayley graphs (that are the basis of Eulerian decoupling). We show
that this structure gives rise to decoupling schemes with bounded-strength
control Hamiltonians that can be applied to composite quantum systems with few
body Hamiltonians and special couplings with the environment. Furthermore, we
show how to construct Eulerian orthogonal arrays having good parameters in
order to obtain efficient decoupling schemes.Comment: 8 pages, revte
Locally D-optimal designs based on a class of composed models resulted from blending Emax and one-compartment models
A class of nonlinear models combining a pharmacokinetic compartmental model
and a pharmacodynamic Emax model is introduced. The locally D-optimal (LD)
design for a four-parameter composed model is found to be a saturated
four-point uniform LD design with the two boundary points of the design space
in the LD design support. For a five-parameter composed model, a sufficient
condition for the LD design to require the minimum number of sampling time
points is derived. Robust LD designs are also investigated for both models. It
is found that an LD design with parameters is equivalent to an LD design
with parameters if the linear parameter in the two composed models is a
nuisance parameter. Assorted examples of LD designs are presented.Comment: Published in at http://dx.doi.org/10.1214/009053607000000776 the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Controlling quantum systems by embedded dynamical decoupling schemes
A dynamical decoupling method is presented which is based on embedding a
deterministic decoupling scheme into a stochastic one. This way it is possible
to combine the advantages of both methods and to increase the suppression of
undesired perturbations of quantum systems significantly even for long
interaction times. As a first application the stabilization of a quantum memory
is discussed which is perturbed by one-and two-qubit interactions
Use of Generalized Fluid System Simulation Program (GFSSP) for Teaching and Performing Senior Design Projects at the Educational Institutions
This paper describes the experience of the authors in using the Generalized Fluid System Simulation Program (GFSSP) in teaching Design of Thermal Systems class at University of Alabama in Huntsville. GFSSP is a finite volume based thermo-fluid system network analysis code, developed at NASA/Marshall Space Flight Center, and is extensively used in NASA, Department of Defense, and aerospace industries for propulsion system design, analysis, and performance evaluation. The educational version of GFSSP is freely available to all US higher education institutions. The main purpose of the paper is to illustrate the utilization of this user-friendly code for the thermal systems design and fluid engineering courses and to encourage the instructors to utilize the code for the class assignments as well as senior design projects
Universal Optimality in Balanced Uniform Crossover Design
Kunert [Ann. Statist. 12 (1984) 1006-1017] proved that, in the class of repeated measurement designs based on t treatments, p = t periods and n = λt experimental units, a balanced uniform design is universally optimal
for direct treatment effects if t ≥ 3 and λ = 1, or if t ≥ 6 and λ = 2. This result is generalized to t ≥ 3 as long as λ ≤ (t −1)/2.Primarily sponsored by NSF Grant DMS-01-03727, National Cancer Institute Grant P01-CA48112-08 and NIH Grant P50-AT00155 ( jointly supported by the National Center for Complementary and Alternative Medicine, the Office of Dietary Supplements, the Office for Research on Women's Health, and the National Institute of General Medicine). The contents are solely the
responsibility of the authors and do not necessarily represent the official views of NIH
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