Information Switching Processor (ISP) contention analysis and control

Future satellite communications, as a viable means of communications and an alternative to terrestrial networks, demand flexibility and low end-user cost. On-board switching/processing satellites potentially provide these features, allowing flexible interconnection among multiple spot beams, direct to the user communications services using very small aperture terminals (VSAT's), independent uplink and downlink access/transmission system designs optimized to user's traffic requirements, efficient TDM downlink transmission, and better link performance. A flexible switching system on the satellite in conjunction with low-cost user terminals will likely benefit future satellite network users

Phase diagrams of period-4 spin chains consisting of three kinds of spins

We study a period-4 antiferromagnetic mixed quantum spin chain consisting of three kinds of spins. When the ground state is singlet, the spin magnitudes in a unit cell are arrayed as (s-t, s, s+t, s) with integer or half-odd integer s and t (0 <= t < s). The spin Hamiltonian is mapped onto a nonlinear sigma model (NLSM) in a previously developed method. The resultant NLSM includes only two independent parameters originating from four exchange constants for fixed s and t. The topological angle in the NLSM determines the gapless phase boundaries between disordered phases in the parameter space. The phase diagrams for various s and t shows rich structures. We systematically explain the phases in the singlet-cluster-solid picture.Comment: 8 pages (16 figures included

Four Wing Flapping Micro Air Vehicles - Dragonies or X-Wings?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83637/1/AIAA-2010-7707-527.pd

Error Measures for Noise-Free Surrogate Approximations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76064/1/AIAA-2008-901-367.pd

Performance Estimate and Simultaneous Application of Multiple Surrogates

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76133/1/AIAA-2006-7047-645.pd

Improving the Hydrodynamic Performance of Diffuser Vanes via Shape Optimization

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77366/1/AIAA-2007-5551-433.pd

Pitfalls of using a single criterion for selecting experimental designs

For surrogate construction, a good experimental design (ED) is essential to simultaneously reduce the effect of noise and bias errors. However, most EDs cater to a single criterion and may lead to small gains in that criterion at the expense of large deteriorations in other criteria. We use multiple criteria to assess the performance of different popular EDs. We demonstrate that these EDs offer different trade-offs, and that use of a single criterion is indeed risky. In addition, we show that popular EDs, such as Latin hypercube sampling (LHS) and D-optimal designs, often leave large regions of the design space unsampled even for moderate dimensions. We discuss a few possible strategies to combine multiple criteria and illustrate them with examples. We show that complementary criteria (e.g. bias handling criterion for variance-based designs and vice versa ) can be combined to improve the performance of EDs. We demonstrate improvements in the trade-offs between noise and bias error by combining a model-based criterion, like the D-optimality criterion, and a geometry-based criterion, like LHS. Next, we demonstrate that selecting an ED from three candidate EDs using a suitable error-based criterion helped eliminate potentially poor designs. Finally, we show benefits from combining the multiple criteria-based strategies, that is, generation of multiple EDs using the D-optimality and LHS criteria, and selecting one design using a pointwise bias error criterion. The encouraging results from the examples indicate that it may be worthwhile studying these strategies more rigorously and in more detail. Copyright © 2007 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/60445/1/2242_ftp.pd

Pointwise RMS bias error estimates for design of experiments

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76728/1/AIAA-2006-724-915.pd

Electronic Structures of Quantum Dots and the Ultimate Resolution of Integers

The orbital angular momentum L as an integer can be ultimately factorized as a product of prime numbers. We show here a close relation between the resolution of L and the classification of quantum states of an N-electron 2-dimensional system. In this scheme, the states are in essence classified into different types according to the m(k)-accessibility, namely the ability to get access to symmetric geometric configurations. The m(k)-accessibility is an universal concept underlying all kinds of 2-dimensional systems with a center. Numerical calculations have been performed to reveal the electronic structures of the states of the dots with 9 and 19 electrons,respectively. This paper supports the Laughlin wave finction and the composite fermion model from the aspect of symmetry.Comment: Two figure

Surrogate Model-Based Strategy for Cryogenic Cavitation Model Validation and Sensitivity Evaluation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76195/1/AIAA-2006-5047-399.pd