A Comparison of Global Optimization Methods for the Design of a High-speed Civil Transport

The conceptual design of aircraft often entails a large number of nonlinear constraints that result in a nonconvex feasible design space and multiple local optima. The design of the high-speed civil transport (HSCT) is used as an example of a highly complex conceptual design with 26 design variables and 68 constraints. This paper compares three global optimization techniques on the HSCT problem and two test problems containing thousands of local optima and noise: multistart local optimizations using either sequential quadratic programming (SQP) as implemented in the design optimization tools (DOT) program or Snyman's dynamic search method, and a modified form of Jones' DIRECT global optimization algorithm. SQP is a local optimizer, while Snyman's algorithm is capable of moving through shallow local minima. The modified DIRECT algorithm is a global search method based on Lipschitzian optimization that locates small promising regions of design space and then uses a local optimizer to converge to the optimum. DOT and the dynamic search algorithms proved to be superior for finding a single optimum masked by noise of trigonometric form. The modified DIRECT algorithm was found to be better for locating the global optimum of functions with many widely separated true local optima.     

Lead-insensitive fiber optic pH sensor and performance under bending

We have designed and tested a lead-insensitive fiber optic pH sensor that is based on the absorption of an indicator dye immobilized in a polymer bead. The fiber optic pH sensor uses two wavelengths; one senses the change in absorption of the indicator dye and the other provides a reference signal. In a view to desired time modulation and the dual wavelength time division multiplexing, we used light emitting diodes for sources, a phototransistor for the detector, and electronics process the detected signal. The sensor has demonstrated fast response, repeatable calibration, reversibility, and stability. This inexpensive device may also be used during bending of the optical fiber for applications in the field.     

Lattice instantons in the large dimension limit

We give a lattice construction of the discretizations of the topologically nontrivial maps S ^2n–1S ⁿ . For n=1, 2, 4, 8, these are the Hopf maps. The construction, based on Barnes-Wall lattices, Reed-Muller error-correcting codes, and Hadamard matrices, generalizes to n=2 ⁱ for i any integer. Manton's result for the cases n=2 and 4 (i.e., the monopole and instanton) are included. We argue that discrete harmonic analysis will be exact in the infinite dimension limit.Work supported in part by the DOE contract #DE-ACO2-87ER-40325.B.Department of Energy Outstanding Junior Investigator supported in part by DOE contract number DE-FGO5-85ER-40226.     

A sensitive,absolute, and time-resolved method for the study of reactive atoms

Laser techniques for the production of free atoms at time t = 0 and their detection at r > 0 have been developed to measure the diffusion of Cs atoms in Ar and the reaction of Cs with O₂ in Ar gas.     

Spectroscopy of francium in a magneto optical trap

The francium atom offers an excellent laboratory to study electron-nucleus interactions. As the heaviest alkali, its atomic properties can be calculated with high precision, and laser trapping methods now allow precision optical spectroscopy of many isotopes. Recent measurements of the 7P_1/2 hyperfine structure, when coupled with previous measurements of the ground state hyperfine structure reveal a hyperfine anomaly. The change in anomaly between an even-N isotope and an odd-N isotope is sensitive to the radial distribution of the neutron magnetization. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electrical properties of ternary molybdates

The possibility of ternary molybdates of compositions Tl₅LnHf(MoO₄)₆ (5 : 1 : 2) (Ln = Dy-Lu), TlLnHf_0.5(MoO₄)₃ (1 : 1 : 1) (Ln = Ce-Nd), and Tl₂LnHf₂(MoO₄)_6.5 (2 : 1 : 4) (Ln = Dy-Lu) was investigated by a method of solid state reactions. A temperature dependence of electrical conductivity in the temperature range 200–500°C was studied.     

Constraining the phase of Bs-Bs mixing

New physics contributions to Bs-Bs mixing can be parametrized by the size (rs2) and the phase (2thetas) of the total mixing amplitude relative to the standard model amplitude. The phase has so far been unconstrained. We first use the D0 measurement of the semileptonic CP asymmetry ASL to obtain the first constraint on the semileptonic CP asymmetry in Bs decays, ASLs=-0.008+/-0.011. Then we combine recent measurements by the CDF and D0 Collaborations--the mass difference (DeltaMs), the width difference (DeltaGammas), and ASL;s--to constrain 2thetas. The errors on DeltaGammas and ASL;s should still be reduced to have a sensitive probe of the phase, yet the central values are such that the regions around 2thetas approximately 3pi/2 and, in particular, 2thetas approximately pi/2, are disfavored.