A Higher-Order Method Implemented in an Unstructured Panel Code to Model Linearized Supersonic Flows

Since their conception in the 1960s, panel codes have remained a critical tool in the design and development of air vehicles. With continued advancement in computational technologies, today\u27s codes are able to solve flow fields around arbitrary bodies more quickly and with higher fidelity than those that preceded them. Panel codes prove most useful during the conceptual design phase of an air vehicle, allowing engineers to iterate designs, and generate full solutions of the flow field around a vehicle in a matter of seconds to minutes instead of hours to days using traditional CFD methods. There have been relatively few panel codes with the capacity to solve supersonic flow fields, and there has been little recently published work done to improve upon them. This work implements supersonic potential flow methods into Cal Poly’s open source panel code, CPanel. CPanel was originally developed to solve steady, subsonic flows utilizing constant strength source and doublet panels to define the geometry, and an unstructured geometry discretization; it was later extended to include viscous vortex particle wakes and transient modeling. In this thesis, a higher-order method is implemented in CPanel for use in solving linearized supersonic flows, where a higher-order method is one that utilizes at least one singularity element whose order is higher than constant. CPanel results are verified against analytical solutions, such as the Taylor-Maccoll solution for supersonic conical flows and 2D shock-expansion theory, and the PANAIR and MARCAP supersonic panel codes. Results correlate well with the analytical solutions, and show strong agreement with the other codes

Organizational Change Considerations for Implementation of Performance-Based Logistics Contracts

Excerpt from the Proceedings of the Nineteenth Annual Acquisition Research SymposiumPerformance-Based Logistics (PBL) administrators have long struggled with developing contracts that result in a win-win relationship for both the contractor and the customer in terms of costs under dynamic conditions, contract length, and sustained performance. These inefficiencies lead to a perpetual cycle of reexamining outdated data, due to current data unavailability, or lack of publications. Thus, outdated practices or cost barriers can often plague outcome-based contracts (OBC). This research entailed seeking out other industries that utilize OBC in asset maintenance. In particular, several state Department of Transportation agencies adopted and successfully implemented Performance-Based Maintenance Contracts (PBMC). In both the qualitative and quantitative spheres, three areas of concern were identified: internal resistance towards performance-based procurement, ineffective relationships between the contractor and customer, and misalignment between contractor performance and scope complexity. After examining 75 contract performance scorecards and conducting interviews with Department of Defense personnel, this research determined that the organizational change required to tackle these specific challenges suggest a paradigm shift in how PBL contracts are implemented and administered.Approved for public release; distribution is unlimited

NaGdF4:Eu3+ Nanoparticles for Enhanced X-ray Excited Optical Imaging.

X-ray luminescent nanoparticles (NPs), including lanthanide fluorides, have been evaluated for application to deep tissue in vivo molecular imaging using optical tomography. A combination of high material density, higher atomic number and efficient NIR luminescence from compatible lanthanide dopant ions indicates that particles that consist of ALnF4 (A = alkaline, Ln = lanthanide element) may offer a very attractive class of materials for high resolution, deep tissue imaging with X-ray excitation. NaGdF4:Eu3+ NPs produced an X-ray excited luminescence that was among the most efficient of nanomaterials that have been studied thus far. We have systematically studied factors such as (a) the crystal structure that changes the lattice environment of the doped Eu3+ ions within the unit cell; and extrinsic factors such as (b) a gold coating (with attendant biocompatibility) that couples to a plasmonic excitation, and (c) changes in the NPs surface properties via changes in the pH of the suspending medium-all with a significant impact on the X-ray excited luminescence of NaGdF4:Eu3+NPs. The luminescence from an optimally doped hexagonal phase NaGdF4:Eu3+ nanoparticle was 25% more intense compared to that of a cubic structure. We observed evidence of plasmonic reabsorption of midwavelength emission by a gold coating on hexagonal NaGdF4:Eu3+ NPs; fortunately, the NaGdF4:Eu3+ @Au core-shell NPs retained the efficient 5D0→7F4 NIR (692 nm) luminescence. The NaGdF4:Eu3+ NPs exhibited sensitivity to the ambient pH when excited by X-rays, an effect not seen with UV excitation. The sensitivity to the local environment can be understood in terms of the sensitivity of the excitons that are generated by the high energy X-rays (and not by UV photons) to crystal structure and to the surface state of the particles

The edge of discovery: Controlling the local false discovery rate at the margin

Despite the popularity of the false discovery rate (FDR) as an error control metric for large-scale multiple testing, its close Bayesian counterpart the local false discovery rate (lfdr), defined as the posterior probability that a particular null hypothesis is false, is a more directly relevant standard for justifying and interpreting individual rejections. However, the lfdr is difficult to work with in small samples, as the prior distribution is typically unknown. We propose a simple multiple testing procedure and prove that it controls the expectation of the maximum lfdr across all rejections; equivalently, it controls the probability that the rejection with the largest p-value is a false discovery. Our method operates without knowledge of the prior, assuming only that the p-value density is uniform under the null and decreasing under the alternative. We also show that our method asymptotically implements the oracle Bayes procedure for a weighted classification risk, optimally trading off between false positives and false negatives. We derive the limiting distribution of the attained maximum lfdr over the rejections, and the limiting empirical Bayes regret relative to the oracle procedure

Shearing Lambs Improves Growth Performance During Periods with Elevated Thermal Load

The purpose of this study was to determine if average daily gain (ADG) is improved in shorn lambs versus non-shorn lambs in the summer months in the upper Midwestern United States. Forty-nine purebred Hampshire and Columbia ram (n = 10 Hampshire and 4 Columbia) and ewe (n = 22 Hampshire and 13 Columbia) lambs were grouped by breed, sex, age (104 ± 1.7 days of age), and initial weight (109 ± 3.5 lbs) into shorn (n=26) and non-shorn (n=23) groups. After shearing (3 June 2004), shorn sheep had approximately 0.1 inches of wool-cover. Lambs were weighed 1, 29, and 57 days following shearing. During the first 28 day period following shearing (period 1), there was no difference in average daily gain between shorn and non-shorn lambs (0.8 ± 0.04 vs 0.82 ± 0.04 lbs/day, respectively). In the second 28 day period (period 2), shorn lambs had a greater average daily gain than non-shorn lambs (1.02 ± 0.06 vs 0.92 ± 0.06 lbs/day, respectively). Period 2 had greater mean (68.9 vs. 63.4 oF, respectively), minimum (59.7 vs 54.1oF, respectively), and maximum (78.2 vs. 73.8oF, respectively) daily ambient air temperature and greater mean humidity (73.97 vs. 68.2 %, respectively) than period 1. The calculated temperature humidity index (THI) was also greater in period 2 than period 1 (66.9 vs. 62.24, respectively). These data indicate that shorn lambs grow more rapidly than non-shorn lambs during periods of elevated temperature, humidity, and THI

Estimation of Multivariate Discrete Hawkes Processes: An Application to Incident Monitoring

Hawkes processes are a class of self-exciting point processes that are used to model complex phenomena. While most applications of Hawkes processes assume that event data occurs in continuous-time, the less-studied discrete-time version of the process is more appropriate in some situations. In this work, we develop methodology for the efficient implementation of discrete Hawkes processes. We achieve this by developing efficient algorithms to evaluate the log-likelihood function and its gradient, whose computational complexity is linear in the number of events. We extend these methods to a particular form of a multivariate marked discrete Hawkes process which we use to model the occurrences of violent events within a forensic psychiatric hospital. A prominent feature of our problem, captured by a mark in our process, is the presence of an alarm system which can be heard throughout the hospital. An alarm is sounded when an event is particularly violent in nature and warrants a call for assistance from other members of staff. We conduct a detailed analysis showing that such a variant of the Hawkes process manages to outperform alternative models in terms of predictive power. Finally, we interpret our findings and describe their implications

Quantising the electromagnetic field in position space

In a recent paper [Southall et al., Locally-acting mirror Hamiltonians, arXiv:1908.07597 (2021)], we showed that it is possible to design locally-acting mirror Hamiltonians which only affect incoming but do not change the dynamics of outgoing wave packets. To better justify our approach, this paper presents a systematic quantisation of the electromagnetic field in position space. Starting from the assumption that the basic building blocks of the electromagnetic field in one dimension are localised bosonic wave packets with a clear direction of propagation -- so-called bosons localised in position (BLiPs) -- we identify the relevant Schroedinger equation and construct Lorentz covariant electric and magnetic field observables. Our description contains the standard description of the quantised electromagnetic field which is shown to apply to a subspace of states.Comment: 15 pages, no figure