Implementing RFID Automation into a Small Scale Aircraft Maintenance System

The purpose of this study was to explore and identify where technology automation could be used to reduce time and wasted labor in aircraft inventory and maintenance processes. The research used passive RFID AutoID technology due to its capabilities in data logging and relatively hands-off, passive use. The Purdue University’s aircraft maintenance system operates under old time card systems with paper inspection, check outs of tools, and non-routine inspections, contributing to long search times when looking for maintenance problems or lost inventory that may have happened up to and over a year ago. Furthermore, there are general inefficiencies due to locating forms and filling out paperwork. This study evaluated the effectiveness of RFID technology in an updated process map of tool / part usage, while providing a proof-of-concept RFID-enabled system to track aircraft inventory parts and tools. The study collected information about tool usage and inventory accountability. The use of a database to facilitate this data tracking would have allowed easy access and analysis for maintenance managers to better identify tool use with individual technicians. The solution was to RFID tag a selected test set of specialized aircraft maintenance tools found in the tool room at Hangar 6 in Purdue University’s airport that require check out (as well as aircraft inventory parts), utilize the RFID tunnel and Alien RFID system at Purdue University’s Supply Chain Lab, attach RFID tags to mock name badges, and allow for tracking simply by walking through the door or near the tunnel and checking if the tool was recorded by the RFID reader for that particular person. This resulted in a study of the “before case” process map to the “after case” process map, and whether any steps were removed or added

Adaptive elliptical aperture photometry: A software package for high-cadence ground-based photometry

Context. Modern space telescopes are currently providing high-precision light curves for a large fraction of the sky, such that many new variable stars are being discovered. However, some stars have periodic variability with periods on the order of minutes and require high-cadence photometry to probe the physical mechanisms responsible. A cadence of less than a minute is often required to remove Nyquist ambiguities and confirm rapid variability, which forces observers to obtain high-cadence ground-based photometry. Aims. We aim to provide a modern software package to reduce ground-based photometric time series data and deliver optimised (differential) light curves. To produce high-quality light curves, which maximise the amplitude signal-to-noise ratio of short-period variability in a Fourier spectrum, we require adaptive elliptical aperture photometry as this represents a significant advantage compared to aperture photometry using circular apertures of fixed radii. Methods. The methodology of our code and its advantages are demonstrated using high-cadence ground-based photometry from the South African Astronomical Observatory (SAAO) of a confirmed rapidly oscillating Ap (roAp) star. Furthermore, we employed our software package to search for rapid oscillations in three candidate roAp stars. Results. We demonstrate that our pipeline represents a significant improvement in the quality of light curves, and we make it available to the community for use with different instruments and observatories. We search for and demonstrate the lack of high-frequency roAp pulsations to a limit of ∼ 1 mmag using B data in the three Ap stars HD 158596, HD 166542, and HD 181810. Conclusions. We demonstrate the significant improvement in the extraction of short-period variability caused by high-frequency pulsation modes, and discuss the implication of null detections in three Ap stars

Nonlinear Scattering of a Bose-Einstein Condensate on a Rectangular Barrier

We consider the nonlinear scattering and transmission of an atom laser, or Bose-Einstein condensate (BEC) on a finite rectangular potential barrier. The nonlinearity inherent in this problem leads to several new physical features beyond the well-known picture from single-particle quantum mechanics. We find numerical evidence for a denumerably infinite string of bifurcations in the transmission resonances as a function of nonlinearity and chemical potential, when the potential barrier is wide compared to the wavelength of oscillations in the condensate. Near the bifurcations, we observe extended regions of near-perfect resonance, in which the barrier is effectively invisible to the BEC. Unlike in the linear case, it is mainly the barrier width, not the height, that controls the transmission behavior. We show that the potential barrier can be used to create and localize a dark soliton or dark soliton train from a phonon-like standing wave.Comment: 15 pages, 15 figures, new version includes clarification of definition of transmission coefficient in general nonlinear vs. linear cas

Measurements of one-point statistics in 21 cm intensity maps via foreground avoidance strategy

Measurements of the one-point probability distribution function and higher-order moments (variance, skewness, and kurtosis) of the high-redshift 21 cm fluctuations are among the most direct statistical probes of the non-Gaussian nature of structure formation and evolution during reionization. However, contamination from astrophysical foregrounds and instrument systematics pose significant challenges in measuring these statistics in real observations. In this work, we use forward modelling to investigate the feasibility of measuring 21 cm one-point statistics through a foreground avoidance strategy. Leveraging the well-known characteristic of foreground contamination in which it occupies a wedge-shape region in k-space, we apply a foreground wedge-cut filter that removes the contaminated modes from a mock data set based on the Hydrogen Epoch of Reionization Array (HERA) instrument, and measure the one-point statistics from the image-space representation of the remaining non-contaminated modes. We experiment with wedge-cutting over different frequency bandwidths and varying degrees of removal that correspond to different assumptions on the extent of the foreground sources on the sky and leakage from the Fourier Transform window function. We find that the centre of the band is the least biased from wedge-cutting while the edges of the band are unusable due to being highly down-weighted by the window function. Based on this finding, we introduce a rolling filter method that allows reconstruction of an optimal wedge-cut 21~cm intensity map over the full bandwidth using outputs from wedge-cutting over multiple sub-bands. We perform Monte Carlo simulations to show that HERA should be able to measure the rise in skewness and kurtosis near the end of reionization with the rolling wedge-cut method if foreground leakage from the Fourier transform window function can be controlled.Comment: 12 pages, 8 figures, submitted to MNRA

What Next-Generation 21 cm Power Spectrum Measurements Can Teach Us About the Epoch of Reionization

A number of experiments are currently working towards a measurement of the 21 cm signal from the Epoch of Reionization. Whether or not these experiments deliver a detection of cosmological emission, their limited sensitivity will prevent them from providing detailed information about the astrophysics of reionization. In this work, we consider what types of measurements will be enabled by a next-generation of larger 21 cm EoR telescopes. To calculate the type of constraints that will be possible with such arrays, we use simple models for the instrument, foreground emission, and the reionization history. We focus primarily on an instrument modeled after the $\sim 0.1~\rm{km}^2$ collecting area Hydrogen Epoch of Reionization Array (HERA) concept design, and parameterize the uncertainties with regard to foreground emission by considering different limits to the recently described "wedge" footprint in k-space. Uncertainties in the reionization history are accounted for using a series of simulations which vary the ionizing efficiency and minimum virial temperature of the galaxies responsible for reionization, as well as the mean free path of ionizing photons through the IGM. Given various combinations of models, we consider the significance of the possible power spectrum detections, the ability to trace the power spectrum evolution versus redshift, the detectability of salient power spectrum features, and the achievable level of quantitative constraints on astrophysical parameters. Ultimately, we find that $0.1~\rm{km}^2$ of collecting area is enough to ensure a very high significance ($\gtrsim30\sigma$) detection of the reionization power spectrum in even the most pessimistic scenarios. This sensitivity should allow for meaningful constraints on the reionization history and astrophysical parameters, especially if foreground subtraction techniques can be improved and successfully implemented.Comment: 27 pages, 18 figures, updated SKA numbers in appendi

Dissection of Anoplophora glabripennis (Coleoptera: Cerambycidae) larval tissues for physiological and molecular studies

Many biological processes are partitioned among organs and tissues, necessitating tissue-specific or organ-specific analysis (particularly for comparative -omics studies). Standardised techniques for tissue identification and dissection are therefore imperative for comparing among studies. Here we describe dissection protocols for isolating six key tissues/organs from larvae of the Asian longhorned beetle, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae): the supraoesophageal ganglion, posterior midgut, hindgut, Malpighian tubules, fat body, and thoracic muscle. We also describe how to extract haemolymph and preserve whole larvae for measurements such as protein, lipid, and carbohydrate content. We include dissection protocols for both fresh-killed and previously frozen specimens. Although this protocol is developed for A. glabripennis, it should allow standardised tissue collection from larvae of other cerambycids and be readily transferrable to other beetle taxa with similar larval morphology

Watching individual molecules flex within lipid membranes using SERS.

Interrogating individual molecules within bio-membranes is key to deepening our understanding of biological processes essential for life. Using Raman spectroscopy to map molecular vibrations is ideal to non-destructively 'fingerprint' biomolecules for dynamic information on their molecular structure, composition and conformation. Such tag-free tracking of molecules within lipid bio-membranes can directly connect structure and function. In this paper, stable co-assembly with gold nano-components in a 'nanoparticle-on-mirror' geometry strongly enhances the local optical field and reduces the volume probed to a few nm(3), enabling repeated measurements for many tens of minutes on the same molecules. The intense gap plasmons are assembled around model bio-membranes providing molecular identification of the diffusing lipids. Our experiments clearly evidence measurement of individual lipids flexing through telltale rapid correlated vibrational shifts and intensity fluctuations in the Raman spectrum. These track molecules that undergo bending and conformational changes within the probe volume, through their interactions with the environment. This technique allows for in situ high-speed single-molecule investigations of the molecules embedded within lipid bio-membranes. It thus offers a new way to investigate the hidden dynamics of cell membranes important to a myriad of life processes.We acknowledge financial support from EPSRC grant EP/G060649/1, EP/I012060/1, ERC grant LINASS 320503. FB acknowledges support from the Winton Programme for the Physics of Sustainability.This is the final published version. It's also available from Nature Publishing at http://www.nature.com/srep/2014/140812/srep05940/full/srep05940.html

Deployable Optical Receiver Array Cubesat

Small satellites and cubesats often have low data transmission rates due to the use of low-gain radio links in UHF and S bands. These links typically provide up to only 1 Mbps for communication between the ground and LEO, limiting the applications and mission operations of small satellites. Optical communication technology can enable much higher data rates and is rapidly gaining hold for larger satellites, including for crosslinks within SpaceX’s Starlink constellation and upcoming NASA deep space missions. However, it has been difficult to implement on small satellites and cubesats due to the need for precision pointing on the order of arcseconds to align the narrow optical laser beam between terminals--a laser transmitter in LEO may yield a footprint less than 100 meters wide at its receiving ground station. We report the development of a 3U cubesat to demonstrate new optical communication technology that eliminates precision pointing accuracy requirements on the host spacecraft. The deployable optical receiver aperture (DORA) aims to demonstrate 1 Gbps data rates over distances of thousands of kilometers. DORA requires an easily accommodated host pointing accuracy of only 10 degrees with minimal stability, allowing the primary mission to continue without reorienting to communicate and/or enabling small satellite missions using low-cost off-the-shelf ADCS systems. To achieve this performance, DORA replaces the traditional receiving telescope on the spacecraft with a collection of wide-angle photodiodes that can identify the angle of arrival for incoming communication lasers and steer the onboard transmitting laser in the corresponding direction. This work is motivated by NASA’s plans for a lunar communications and navigation network and supported by NASA’s Space Technology Program (STP). It is ideally suited for crosslink communications among small spacecraft, especially for those forming a swarm and/or a constellation, and for surface to orbit communications. We will implement the deployable optical receiver aperture and miniature transmission telescope as a 1U payload in the 3U cubesat and conduct the demonstration flight in LEO. Future implementations of the DORA technology are expected to further enable omnidirectional receiving of multiple optical communications simultaneously and accommodate multiple transmitting modules on a single cubesat

Topology and Ground State Control In Open-Shell Donor-Acceptor Conjugated Polymers

Donor-acceptor (DA) conjugated polymers (CPs) with narrow bandgaps and open-shell (diradical) character represent an emerging class of materials whose rich behavior emanates from their collective electronic properties and diminished electron pairing. However, the structural and electronic heterogeneities that define these materials complicate bandgap control at low energies and connections linking topology, exchange interactions, and (opto)electronic functionality remain nascent. To address these challenges, we demonstrate structurally rigid and strongly π-conjugated copolymers comprised of a solubilizing thiadiazoloquinoxaline acceptor and cyclopenta[2,1-b:3,4-b′]dithiophene or dithieno[3,2-b:2′,3′-d]thiophene donors. Atom-specific substitution modulates local aromatic character within the donor resulting in dramatic differences in structural, physicochemical, electronic, and magnetic properties of the polymers. These long-range π-mediated interactions facilitate control between low-spin aromatic and high-spin quinoidal forms. This work provides a strategy to understand the evolution of the electronic structure within DA CPs, control the ground state spin multiplicity, tune spin-spin interactions, and articulate the emergence of their novel properties