Design optimization using multiple dominance relations

A challenge in engineering design is to choose suitable objectives and constraints from many quantities of interest, while ensuring an optimization is both meaningful and computationally tractable. We propose an optimization formulation that can take account of more quantities of interest than existing formulations, without reducing the tractability of the problem. This formulation searches for designs that are optimal with respect to a binary relation within the set of designs that are optimal with respect to another binary relation. We then propose a method of finding such designs in a single optimization by defining an overall ranking function to use in optimizers, reducing the cost required to solve this formulation. In a design under uncertainty problem, our method obtains the most robust design that is not stochastically dominated faster than a multiobjective optimization. In a car suspension design problem, our method obtains superior designs according to a k-optimality condition than previously suggested multiobjective approaches to this problem. In an airfoil design problem, our method obtains designs closer to the true lift/drag Pareto front using the same computational budget as a multiobjective optimization.     

Generalized information reuse for optimization under uncertainty with non‐sample average estimators

In optimization under uncertainty for engineering design, the behavior of the system outputs due to uncertain inputs needs to be quantified at each optimization iteration, but this can be computationally expensive. Multifidelity techniques can significantly reduce the computational cost of Monte Carlo sampling methods for quantifying the effect of uncertain inputs, but existing multifidelity techniques in this context apply only to Monte Carlo estimators that can be expressed as a sample average, such as estimators of statistical moments. Information reuse is a particular multifidelity method that treats previous optimization iterations as lower fidelity models. This work generalizes information reuse to be applicable to quantities whose estimators are not sample averages. The extension makes use of bootstrapping to estimate the error of estimators and the covariance between estimators at different fidelities. Specifically, the horsetail matching metric and quantile function are considered as quantities whose estimators are not sample averages. In an optimization under uncertainty for an acoustic horn design problem, generalized information reuse demonstrated computational savings of over 60% compared with regular Monte Carlo sampling.     

Versatile pattern generation of periodic,high aspect ratio Si nanostructure arrays with sub-50-nm resolution on a wafer scale

We report on a method of fabricating variable patterns of periodic, high aspect ratio silicon nanostructures with sub-50-nm resolution on a wafer scale. The approach marries step-and-repeat nanoimprint lithography (NIL) and metal-catalyzed electroless etching (MCEE), enabling near perfectly ordered Si nanostructure arrays of user-defined patterns to be controllably and rapidly generated on a wafer scale. Periodic features possessing circular, hexagonal, and rectangular cross-sections with lateral dimensions down to sub-50 nm, in hexagonal or square array configurations and high array packing densities up to 5.13 × 10⁷ structures/mm² not achievable by conventional UV photolithography are fabricated using this top-down approach. By suitably tuning the duration of catalytic etching, variable aspect ratio Si nanostructures can be formed. As the etched Si pattern depends largely on the NIL mould which is patterned by electron beam lithography (EBL), the technique can be used to form patterns not possible with self-assembly methods, nanosphere, and interference lithography for replication on a wafer scale. Good chemical resistance of the nanoimprinted mask and adhesion to the Si substrate facilitate good pattern transfer and preserve the smooth top surface morphology of the Si nanostructures as shown in TEM. This approach is suitable for generating Si nanostructures of controlled dimensions and patterns, with high aspect ratio on a wafer level suitable for semiconductor device production.     

Changes in cognitive content during and following cognitive therapy for recurrent depression: Substantial and enduring, but not predictive of change in depressive symptoms.

The authors examined the amount and durability of change in the cognitive content of 156 adult outpatients with recurrent major depressive disorder after treatment with cognitive therapy. The pre-post magnitude of change was large for the Attributional Style Questionnaire Failure composite (d = 0.79), Dysfunctional Attitudes Scale (d = 1.05), and Self-Efficacy Scale (d = 0.83), and small for the Attributional Style Questionnaire Success composite (d = 0.30). Changes in cognitive content were clinically significant, as defined by their 64%-87% scores overlapping with score distributions from community dwellers. Improvement was durable over a 2-year follow-up. Changes in negative cognitive content could be detected early and distinguished responders from nonresponders. In responders, continuation-phase cognitive therapy was associated with further improvements on only 1 measure of cognitive content. Early changes in negative cognitive content did not predict later changes in depressive symptoms, which the authors discuss in the context of methodological challenges and the cognitive theory of depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

DNA vaccination affords significant protection against feline immunodeficiency virus infection without inducing detectable antiviral antibodies

To test the potential of a multigene DNA vaccine against lentivirus infection, we generated a defective mutant provirus of feline immunodeficiency virus (FIV) with an in-frame deletion in pol (FIVDeltaRT). In a first experiment, FIVDeltaRT DNA was administered intramuscularly to 10 animals, half of which also received feline gamma interferon (IFN-gamma) DNA. The DNA was administered in four 100-microg doses at 0, 10, and 23 weeks. Immunization with FIVDeltaRT elicited cytotoxic T-cell (CTL) responses to FIV Gag and Env in the absence of a serological response. After challenge with homologous virus at week 26, all 10 of the control animals became seropositive and viremic but 4 of the 10 vaccinates remained seronegative and virus free. Furthermore, quantitative virus isolation and quantitative PCR analysis of viral DNA in peripheral blood mononuclear cells revealed significantly lower virus loads in the FIVDeltaRT vaccinates than in the controls. Immunization with FIVDeltaRT in conjunction with IFN-gamma gave the highest proportion of protected cats, with only two of five vaccinates showing evidence of infection following challenge. In a second experiment involving two groups (FIVDeltaRT plus IFN-gamma and IFN-gamma alone), the immunization schedule was reduced to 0, 4, and 8 weeks. Once again, CTL responses were seen prior to challenge in the absence of detectable antibodies. Two of five cats receiving the proviral DNA vaccine were protected against infection, with an overall reduction in virus load compared to the five infected controls. These findings demonstrate that DNA vaccination can elicit protection against lentivirus infection in the absence of a serological response and suggest the need to reconsider efficacy criteria for lentivirus vaccines.     

High resolution solution and solid state NMR characterization of ethylene/1-butene and ethylene/1-hexene copolymers fractionated by preparative temperature rising elution fractionation

Preparative TREF was used to fractionate 2 commercial LLDPE polymers. These polymers had similar MFI values, density and comonomer content, but differed in comonomer type, 1-butene vs 1-hexene. High resolution solution NMR and solid state NMR was used to characterize the copolymer fractions. Distinct differences in chemical composition distribution could be observed from solution NMR results, and these correlated well with solid state analyses. Conclusions regarding the molecular make-up and crystallization phenomena are made.     

The Bedford survey: ten year mortality rates in newly diagnosed diabetics, borderline diabetics and normoglycaemic controls and risk indices for coronary heart disease in borderline diabetics

Mortality rates from coronary heart disease and from all causes have been ascertained over ten years in three groups of people participating in the Bedford Survey--newly-diagnosed diabetics, borderline diabetics and control subjects with normal glucose tolerance. Age corrected mortality rates, from all causes and coronary heart disease, were highest in the diabetics and intermediate in the borderline diabetics and in both groups were similar in men and women. When statistical allowance was made for baseline differences in age, blood pressure and obesity, female borderline diabetics still had a significantly increased risk over their controls of death from 'all causes'. Much of the difference appeared to be due to a relative excess of deaths due to coronary heart disease. It is concluded that borderline diabetes (or impaired glucose tolerance) is associated with a relatively greater increase in mortality risk in women than men. During the 10-year follow-up of the Bedford borderline diabetics, coronary heart disease morbidity and mortality rates were similar in men and women. Age at entry to the study was the major independent and significant predictor of mortality from all causes. The level of systolic blood pressure and current cigarette smoking at baseline were statistically significant predictors only of mortality due to coronary heart disease.     

Effects of Cobalt on Structure,Microchemistry and Properties of a Wrought Nickel-Base Superalloy

Cobalt in a 17 pct cobalt containing wrought nickel-base superalloy is systematically substituted for by nickel in order to determine the role of cobalt. The eventual goal is to reduce the levels of cobalt, a critical strategic element, in superalloys. It is found that the strengthening γ microstructure is highly heat treatment sensitive. Reducing cobalt did not result in a reduction of the fine γ precipitates after a coarse grain type (blading) heat treatment, but did after a fine grain type (disk) heat treatment. Representative mechanical properties were determined for each case to isolate microstructural and microchemistry effects. Ambient yield strength and tensile strength were seen to decrease by no more than 15 pct and 7 pct, respectively, even when all the cobalt was removed. The decrease in strength is quantitatively discussed and shown to be consistent with the observed microstructural results and microchemistry results obtained using STEM/EDS. Elevated temperature creep and stress rupture resistances were concluded to be affected by alloy cobalt content through its effect on strengthening γ volume fraction. Significant decreases in these properties were observed for the lower cobalt content alloys. Long term aging, precipitate coarsening, and carbide stability results are also presented and discussed.     

A method for deriving viscoelastic modulus for skeletal muscle from transient pulse propagation

In the studies of viscoelastic wave propagation, the use of transient pulses offers several advantages over that of steady state sinusoidal waves, especially with regards to problems due to wave reflections and to repeated testing for different frequencies.