BYU Represents at DPS

We present an undergraduate optics instructional laboratory designed to teach skills relevant to a broad range of modern scientific and technical careers. In this laboratory project, students image a custom aperture using coherent diffraction imaging, while learning principles and skills related to digital image processing and computational imaging, including multidimensional Fourier analysis, iterative phase retrieval, noise reduction, finite dynamic range, and sampling considerations. After briefly reviewing these imaging principles, we describe the required experimental materials and setup for this project. Our experimental apparatus is both inexpensive and portable, and a software application we developed for interactive data analysis is freely available.

A sound power spectrum analysis has been conducted on a T-7A-installed F404 engine, for operating conditions spanning intermediate thrust to afterburner. From free-field pressure spectra at microphone arc arrays with radii of 38 and 76 m, sound power level spectra are calculated from surface integrals and assumed axisymmetric radiation. The spectral peak-frequency region, from ∼100–500 Hz, broadens with increasing engine conditions. When the power level spectra are plotted with Strouhal number, the spectral peak decreases with engine condition. Comparing this decrease with rocket data suggests that military jet noise radiation is becoming more rocket-like, especially at afterburner conditions.

Understanding the atomic structure of precipitate phases in shape memory alloys is critical to determining their structure–property relationships and developing high-performance shape memory alloys. However, experimental methods are limited in determining atomic configurations in cases where the number of atoms per unit cell is very high, or the phase is small (few nms). While density functional theory (DFT) can aid in the accurate determination of a phase’s crystallography, this is challenged by the number of candidate structures. Recently, a cubic phase was discovered during the heat treatment of a Hf-Ni-Ti alloy developed with improved tribological applications and rolling contact fatigue. We use DFT, machine learned interatomic potentials (MLIPs), and a genetic algorithm to identify likely configurations for the cubic phase. Likely candidate structures consistent with experimentally determined structural information were identified. Limitations of experimental microscopy methods, crystal simulation, and DFT-MLIP techniques are discussed.

We analyze three nearby spiral galaxies—NGC 1097, NGC 1566, and NGC 3627—using images from the DustPedia database in seven infrared bands (3.6, 8, 24, 70, 100, 160, and 250 μm). For each image, we perform photometric decomposition and construct a multi-component model, including a detailed representation of the spiral arms. Our results show that the light distribution is well described by an exponential disk and a Sérsic bulge when non-axisymmetric components are properly taken into account. We test the predictions of the stationary density wave theory using the derived models in bands, tracing both old stars and recent star formation. Our findings suggest that the spiral arms in all three galaxies are unlikely to originate from stationary density waves. Additionally, we perform spectral energy distribution (SED) modeling using the hierarchical Bayesian code HerBIE, fitting individual components to derive dust properties. We find that spiral arms contain a significant (>10%) fraction of cold dust, with an average temperature of approximately 18–20 K. The estimated fraction of polycyclic aromatic hydrocarbons (PAHs) declines significantly toward the galactic center but remains similar between the arm and interarm regions.

X-ray reverberation mapping is a powerful technique for probing the innermost accretion disk, whereas continuum reverberation mapping in the UV, optical, and infrared (UVOIR) reveals reprocessing by the rest of the accretion disk and broad-line region (BLR). We present the time lags of Mrk 817 as a function of temporal frequency measured from 14 months of high-cadence monitoring from Swift and ground-based telescopes, in addition to an XMM-Newton observation, as part of the AGN STORM 2 campaign. The XMM-Newton lags reveal the first detection of a soft lag in this source, consistent with reverberation from the innermost accretion flow. These results mark the first simultaneous measurement of X-ray reverberation and UVOIR disk reprocessing lags—effectively allowing us to map the entire accretion disk surrounding the black hole. Similar to previous continuum reverberation mapping campaigns, the UVOIR time lags arising at low temporal frequencies are longer than those expected from standard disk reprocessing by a factor of 2–3. The lags agree with the anticipated disk reverberation lags when isolating short-timescale variability, namely timescales shorter than the Hβ lag. Modeling the lags requires additional reprocessing constrained at a radius consistent with the BLR size scale inferred from contemporaneous Hβ-lag measurements. When we divide the campaign light curves, the UVOIR lags show substantial variations, with longer lags measured when obscuration from an ionized outflow is greatest. We suggest that, when the obscurer is strongest, reprocessing by the BLR elongates the lags most significantly. As the wind weakens, the lags are dominated by shorter accretion disk lags.

Pulsatile bioimpedance measurements require filters with very narrow bandwidths to preserve heartbeat-rate modulation while suppressing excess noise. At the signal's carrier frequency, this demands an impractically-high-Q filter. Multirate signal processing is an attractive solution to this problem, as it provides an avenue to extract the signals of interest practically. This paper presents a multirate filtering solution and shows step-by-step how the bioimpedance data of interest are extracted from noise and excitation frequency in in-phase and quadrature signals acquired from an analog measurement circuit. The tested impedance values resemble realistic human tissue impedance, demonstrating the method's ability to measure a human pulse within an approximately 50−Hz bandwidth at a 1−MHz carrier. This method is useful for high-Q bioimpedance measurements where interest lies in the details of signals pulsing at the rate of a beating human heart.