2017 Baccalaureate Mass Homily

Homily delivered at the 2017 Baccalaureate Mass as part of the 171st Commencement of the College of the Holy Cross. The homilist, Rev. Michael Rogers, S.J., is a member of the College\u27s Chaplain\u27s Office and College Ministry Center. He is also an alumnus of the Holy Cross Class of 2002.https://crossworks.holycross.edu/bacc_homily/1000/thumbnail.jp

Active vibration control (AVC) of a satellite boom structure using optimally positioned stacked piezoelectric actuators

In this paper, results for active vibration control predicted from experimental measurements on a lightweight structure are compared with purely computational predictions. The structure studied is a 4.5m long satellite boom consisting of 10 identical bays with equilateral triangular cross sections. First, the results from a Fortran code that is based on a receptance analysis are validated against the experimental forced response of the boom structure. Exhaustive searches are then carried out to find the optimum positions for one and two actuators. Finally, a genetic algorithm is employed to find high-quality positions for three actuators on the structure that will achieve the greatest reductions in vibration transmission. Having found these actuator positions, experiments are then carried out to verify the quality of the theoretical predictions. It was found that the attenuation achievable in practice for one, two and three actuators were, respectively, 15.1, 26.1 and 33.5 dB

Active vibration control (AVC) of a satellite boom structure using optimally positioned stacked piezoelectric actuators

In this paper, results for active vibration control predicted from experimental measurements on a lightweight structure are compared with purely computational predictions. The structure studied is a 4.5m long satellite boom consisting of 10 identical bays with equilateral triangular cross sections. First, the results from a Fortran code that is based on a receptance analysis are validated against the experimental forced response of the boom structure. Exhaustive searches are then carried out to find the optimum positions for one and two actuators. Finally, a genetic algorithm is employed to find high-quality positions for three actuators on the structure that will achieve the greatest reductions in vibration transmission. Having found these actuator positions, experiments are then carried out to verify the quality of the theoretical predictions. It was found that the attenuation achievable in practice for one, two and three actuators were, respectively, 15.1, 26.1 and 33.5 dB

Symptoms at lung cancer diagnosis are associated with major differences in prognosis

We report a cohort study of survival of patients with lung cancer presenting to a single multidisciplinary team between 1997 and 2011, according to symptoms at presentation. The overall median survival of the 3800 lung cases was 183 days (95% CI 171 to 195). There was a statistically significant difference in survival between the 12 symptom groups identified both without and with adjustment for the prognostic variables of age, gender and histology (P<0.001). Compared with the cough-alone symptom group, the risks of dying or HRs were significantly higher for the groups presenting with breathlessness (HR 1.86, 95% CI 1.54 to 2.24, n=359), systemic symptoms (HR 1.91, 95% CI 1.48 to 2.45, n=95), weight loss (HR 2.46, 95% CI 1.90 to 3.18, n=106), chest pain (HR 1.96, 95% CI 1.56 to 2.45, n=159), cough with breathlessness (HR 1.59 95% CI 1.28 to 1.98, n=177), neurological symptoms (HR 3.07, 95% CI 2.45 to 3.84, n=155) and other symptom combinations (HR 2.05, 95% CI 1.75 to 2.40, n=1963). Cough may deserve particular prominence in public health campaigns

Distributions of fatigue damage from data-driven strain prediction using Gaussian process regression

Fatigue is a leading cause of structural failure; however, monitoring and prediction of damage accumulation remains an open problem, particularly in complex environments where maintaining sensing equipment is challenging. As a result, there is a growing interest in virtual loads monitoring, or inferential sensing, particularly for predicting strain in areas of interest using machine learning methods. This paper pursues a probabilistic approach, relying on a Gaussian process (GP) regression, to produce both strain predictions and a predictive distribution of the accumulated fatigue damage in a given time period. Here, the fatigue distribution is achieved via propagation of successive draws from the posterior GP through a rainflow count. The establishment of such a distribution crucially accounts for uncertainty in the predictive model and will form a valuable element in any probabilistic risk assessment. For demonstration of the method, distributions for predicted fatigue damage in an aircraft wing are produced across 84 flights. The distributions provide a robust measure of predicted damage accumulation and model uncertainty

Wilson Lines off the Light-cone in TMD PDFs

Transverse Momentum Dependent (TMD) parton distribution functions (PDFs) also take into account the transverse momentum ($p_T$) of the partons. The $p_T$-integrated analogues can be linked directly to quark and gluon matrix elements using the operator product expansion in QCD, involving operators of definite twist. TMDs also involve operators of higher twist, which are not suppressed by powers of the hard scale, however. Taking into account gauge links that no longer are along the light-cone, one finds that new distribution functions arise. They appear at leading order in the description of azimuthal asymmetries in high-energy scattering processes. In analogy to the collinear operator expansion, we define a universal set of TMDs of definite rank and point out the importance for phenomenology.Comment: 12 pages, presented by the first author at the Light-Cone Conference 2013, May 20-24, 2013, Skiathos, Greece. To be published in Few Body System

A spectrum of physics-informed Gaussian processes for regression in engineering

Despite the growing availability of sensing and data in general, we remain unable to fully characterize many in-service engineering systems and structures from a purely data-driven approach. The vast data and resources available to capture human activity are unmatched in our engineered world, and, even in cases where data could be referred to as “big,” they will rarely hold information across operational windows or life spans. This paper pursues the combination of machine learning technology and physics-based reasoning to enhance our ability to make predictive models with limited data. By explicitly linking the physics-based view of stochastic processes with a data-based regression approach, a derivation path for a spectrum of possible Gaussian process models is introduced and used to highlight how and where different levels of expert knowledge of a system is likely best exploited. Each of the models highlighted in the spectrum have been explored in different ways across communities; novel examples in a structural assessment context here demonstrate how these approaches can significantly reduce reliance on expensive data collection. The increased interpretability of the models shown is another important consideration and benefit in this context

Experimental and theoretical studies of transport through large scale, partially aligned arrays of single-walled carbon nanotubes in thin film type transistors

Gate-modulated transport through partially aligned films of single-walled carbon nanotubes (SWNTs) in thin film type transistor structures are studied experimentally and theoretically. Measurements are reported on SWNTs grown by chemical vapor deposition with systematically varying degrees of alignment and coverage in transistors with a range of channel lengths and orientations perpendicular and parallel to the direction of alignment. A first principles stick-percolation-based transport model provides a simple, yet quantitative framework to interpret the sometimes counterintuitive transport parameters measured in these devices. The results highlight, for example, the dramatic influence of small degrees of SWNT misalignment on transistor performance and imply that coverage and alignment are correlated phenomena and therefore should be simultaneously optimized. The transport characteristics reflect heterogeneity in the underlying anisotropic metal-semiconductor stick-percolating network and cannot be reproduced by classical transport models. © 2007 American Chemical Society