Thermoelastic assessment of damage growth in composites

This paper examines, experimentally and numerically, the use of thermal emission measurements as a means of assessing severity of damage and monitoring damage growth in composite materials. In contrast to most traditional methods the thermal emission profile reflects the interaction of load, geometry, material and damage in a non-destructive fashion. It represents a possible method for the scaling of test data, obtained from coupon tests, to tests on full scale structures.     

32P-postlabeling detection of DNA adducts in fish from chemically contaminated waterways

Fish were collected from sites in the chemically-contaminated Buffalo River, New York, and the Detroit River, Michigan. The sediments of these rivers have high levels of chemical contaminants, including polycyclic aromatic hydrocarbons (PAHs), and fish from these locations have high prevalences of liver cancer. To determine chemical-DNA interactions and a possible role for chemicals as a cause of the observed tumors, DNA was isolated from livers and was enzymatically digested to normal and adducted nucleotides. The DNA digests were enriched for hydrophobic, bulky adducts, either by preparative reverse phase high pressure liquid chromatography, or by selective nuclease P1 dephosphorylation of normal nucleotides. DNA-chemical adducts were then quantitated by 32P-postlabeling analysis. Regardless of the adduct enrichment procedure, the chromatograms derived from DNA of fish from polluted areas showed a diffuse, diagonal radioactive zone consisting, at least in part, of multiple overlapping discrete adduct spots. The behavior of the adducts in the diagonal radioactive zone and of their unlabeled precursors is consistent with their identification as nucleotide adducts of a variety of bulky, hydrophobic, aromatic genotoxic compounds. Analysis of bile demonstrated recent exposure to multi-ringed aromatic compounds.     

Item response theory modeling of substance use: An index based on 10 drug categories.

This study examined the psychometric characteristics of an index of substance use involvement using item response theory. The sample consisted of 292 men and 140 women who qualified for a Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.; American Psychiatric Association, 1987) substance use disorder (SUD) diagnosis and 293 men and 445 women who did not qualify for a SUD diagnosis. The results indicated that men ha4 a higher probability of endorsing substance use compared with women. The index significantly predicted health, psychiatric, and psychosocial disturbances as well as level of substance use behavior and severity of SUD after a 2-year follow-up. Finally, this index is a reliable and useful prognostic indicator of the risk for SUD and the medical and psychosocial sequelae of drug consumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Internet2 QBone: building a testbed for differentiated services

The Internet2 project is a partnership of over 130 U.S. universities, 40 corporations, and 30 other organizations. Since its inception, one of the primary technical objectives of Internet2 has been to engineer scalable, interoperable, and administrable interdomain QoS to support an evolving set of new advanced networked applications. Applications like distance learning, remote instrument access and control, advanced scientific visualization, and networked collaboratories will allow universities to fulfill their research and education missions into the future, but only if the network QoS these applications require can be ensured. To meet this challenge, the Internet2 QBone initiative has brought together a dedicated group of U.S. university and federal agency networks, international research networks, engineers, researchers, and applications developers to build a testbed for interdomain IP differentiated services. This article presents the engineering motivations behind DiffServ and its adoption by Internet2, provides an overview of the QBone architecture, and describes its anticipated deployment, including plans for a trial inter-domain bandwidth brokering architecture. Security aspects are considered togethered together with an inter-bandwidth broker reservation signaling protocol     

Christopher Strachey—Understanding Programming Languages

Higher-Order and Symbolic Computation -     

Transient dynamics of CW intracavity singly resonant opticalparametric oscillators

We study the transient dynamics of CW intracavity, singly-resonant optical parametric oscillators (ICSROs). Relaxation oscillations of the 1064-nm pump light are measured, in both the presence and absence of parametric conversion, in a periodically poled LiNbO₃ (PPLN) CW ICSRO pumped intracavity to a Nd:YVO₄ laser. The presence of parametric conversion is shown to significantly increase both the damping times and oscillation frequencies of the dynamics; at three times the parametric oscillator threshold, these take values of 200 μs and 2 MHz, respectively. Oscillation frequencies are shown to be in good agreement with theoretical values. The influence of energy diffusion and thermal lensing are analyzed to account for discrepences between measured and theoretical damping times. We discuss the implications of the dynamic behavior to the stable-power operation of CW ICSROs     

A Computational Design Methodology for Assembly and Actuation of Thin-Film Structures via Patterning of Eigenstrains

We develop a computational approach to design 3-D structures that can be fabricated and then assembled and/or actuated by spatially tailoring the layout of multilayer films with eigenstrains. Eigenstrains are stress-free strains when they occur in an unconstrained solid. They are almost an inevitable companion, albeit often unwanted, of thin-film processes. When they vary through the thickness, the constraint of the layers leads to internal stresses and bending and buckling deformations can occur; when they additionally vary in the plane of the film, more complex deformations can result. To advantageously use this phenomenon, we build on relatively simple mechanics ideas in a continuum formulation and combine geometrically nonlinear finite-element analysis of arbitrary-shaped multilayer films with a topology optimization methodology to determine the material layout in each layer so the film deforms into a prescribed shape. We expand our previous experimentally validated approach to include initially curved films and anisotropic eigenstrains. Using an extended system formulation for directly computing instability points allows us to tailor postbuckling response while explicitly controlling the design at limit and bifurcation points. We demonstrate the potential and versatility of our approach by applying it to a series of problems of contemporary and emerging interest.     

The feasibility of a mixed reality surgical training environment

The Sheffield knee arthroscopy training system (SKATS) was originally a visual-based virtual environment without haptic feedback, but has been further developed as a mixed reality-training environment through the use of tactile augmentation (or passive haptics). The design of the new system is outlined and then tested. In the first experiment described, the effect of tactile augmentation on performance is considered by comparing novice performance using the original and mixed reality system. In the second experiment the mixed reality system is assessed in terms of construct validity by comparing the performance of users with differing levels of surgical expertise. The results are discussed in terms of the validity of a mixed reality environment for training knee arthroscopy.